Ion Implantation

The growth of vertically aligned carbon nanotubes using a direct current plasma enhanced chemical vapor deposition system is reported. The growth properties are studied as a function of the Ni catalyst layer thickness, bias voltage, deposition temperature, C 2 H 2 :NH 3 ratio, and pressure. It was found that the diameter, growth rate, and areal density of the nanotubes are controlled by the initial thickness of the catalyst layer. The alignment of the nanotubes depends on the electric field. Our results indicate that the growth occurs by diffusion of carbon through the Ni catalyst particle, which rides on the top of the growing tube.

Implanted B and P dopants in Si exhibit transient enhanced diffusion ͑TED͒ during annealing which arises from the excess interstitials generated by the implant. In order to study the mechanisms of TED, transmission electron microscopy measurements of implantation damage were combined with B diffusion experiments using doping marker structures grown by molecular-beam epitaxy ͑MBE͒. Damage from nonamorphizing Si implants at doses ranging from 5ϫ10 12 to 1ϫ10 14 /cm 2 evolves into a distribution of ͕311͖ interstitial agglomerates during the initial annealing stages at 670-815°C. The excess interstitial concentration contained in these defects roughly equals the implanted ion dose, an observation that is corroborated by atomistic Monte Carlo simulations of implantation and annealing processes. The injection of interstitials from the damage region involves the dissolution of ͕311͖ defects during Ostwald ripening with an activation energy of 3.8Ϯ0.2 eV. The excess interstitials drive substitutional B into electrically inactive, metastable clusters of presumably two or three B atoms at concentrations below the solid solubility, thus explaining the generally observed immobile B peak during TED of ion-implanted B. Injected interstitials undergo retarded diffusion in the MBE-grown Si with an effective migration energy of ϳ3.5 eV, which arises from trapping at substitutional C. The concept of trap-limited diffusion provides a stepping stone for understanding the enormous disparity among published values for the interstitial diffusivity in Si. The population of excess interstitials is strongly reduced by incorporating substitutional C in Si to levels of ϳ10 19 /cm 3 prior to ion implantation. This provides a promising method for suppressing TED, thus enabling shallow junction formation in future Si devices through dopant implantation. The present insights have been implemented into a process simulator, allowing for a significant improvement of the predictive modeling of TED.

Carbon nanotube field-effect transistors ͑CNTFETs͒ fabricated out of as-grown nanotubes are unipolar p-type devices. Two methods for their conversion from p-to n-type devices are presented. The first method involves conventional doping with an electron donor, while the second consists of annealing the contacts in vacuum to remove adsorbed oxygen. A comparison of these methods shows fundamental differences in the mechanism of the transformation. The key finding is that the main effect of oxygen adsorption is not to dope the bulk of the tube, but to modify the barriers at the metal-semiconductor contacts. The oxygen concentration and the level of doping of the nanotube are therefore complementary in controlling the CNTFET characteristics. Finally, a method of controlling individually the contact barriers by local heating is demonstrated.

A threshold-shifting, single transistor memory structure with fast read and write times and long retention time is described. The structure consists of a silicon field-effect transistor with nano-crystals of germanium or silicon placed in the gate oxide in close proximity of the inversion surface. Electron charge is stored in these isolated 2-5 nm size nano-crystals which are separated from each other by greater than 5 nm of Si02 and from the inversion layer of the substrate surface by less than 5 nm of Si02. Direct tunneling of charge from the inversion layer and its storage in the nano-crystal causes a shift in the threshold voltage which is detected via current sensing. The nano-crystals are formed using implantation and annealing or using direct deposition of the distributed floating gate region. Threshold shift of 0.3 V is obtained in Ge-implanted devices with 2 nm of Si02 injection layer by a 4 V write pulse of 300 ns duration. The nanocrystal memories achieve improved programming characteristics as a nonvolatile memory as well as simplicity of the single poly-Sigate process. The VT window is scarcely degraded after greater than lo9 writelerase cycles or greater than lo5 s retention time.

COMPLEMENTARY MOS integrated circuits are attractive for micropower digital systems since their standby or static power drain is lower than that of any other type of digital circuit. Because the dynamic power consumed during their switching transients is proportional to the supply voltage squared, it is often desirable to operate CMOS circuits at as low a supply voltage as practical. Low voltage operation is particularly useful where battery operation is necessary such as in implanted biomedical devices and electronic wristwatches.

Electronic spectra Positron annihilation lifetime spectroscopy a b s t r a c t Molecular charge-transfer complexes of the tetramethylethylenediamine (TMEDA) with picric acid (Pi-OH), benzene-1,4-diol (QL), tin(IV) tetrachloride (SnCl 4 ), iodine, bromine, and zinc chloride (ZnCl 2 ) have been synthesized and investigated by elemental and thermal analysis, electronic, infrared, Raman and proton-NMR, energy-dispersive X-ray spectroscopy, X-ray powder diffraction and positron annihilation lifetime spectroscopy, and scanning electron microscopy. In this work, three types of acceptors p-acceptors (Pi-OH and QL), r-acceptors (iodine and bromine), and vacant orbital acceptors (SnCl 4 and ZnCl 2 ) were covered. The results of elemental analysis indicated that the CT complexes were formed with ratios 1:1 and 1:2 for QL, SnCl 4 , and ZnCl 2 acceptors and iodine, Pi-OH, and Br 2 acceptors, respectively. The type of chelating between the TMEDA donor and the mentioned acceptors depends upon the behavior of both items. The positron annihilation lifetime parameters were found to be dependent on the structure, electronic configuration, and the power of acceptors. The correlation between these parameters and the molecular weight and biological activities of studied complexes was also observed. Regarding the electrical properties, the AC conductivity and the dielectric coefficients were measured as a function of frequency at room temperature. The TMEDA charge-transfer complexes were screened against antibacterial (Escherichia coli, Staphylococcus aureus, Bacillus subtilis, and Pseudomonas aeruginosa) and antifungal (Aspergillus flavus and Candida albicans) activities.

Some probe catalytic photooxidation reactions with aliphatic and aromatic organic compounds having different acid strengths, i.e. methanoic acid, ethanoic acid, benzoic acid and 4-nitrophenol, were carried out in aqueous systems by using polycrystalline TiO 2 powders doped with various transition metal ions (Co, Cr, Cu, Fe, Mo, V and W). The Co-doped powder showed to be more photoactive than the bare TiO 2 for methanoic acid degradation while the behaviour of TiO 2 /Cu and TiO 2 /Fe was similar to that of the support. TiO 2 /W was the most efficient sample for the photodegradation of benzoic acid and 4-nitrophenol, TiO 2 the most active powder for ethanoic acid. A tentative explanation is provided by taking into account: (i) the dissociation constants (K a ) of the different acids used as substrates; (ii) their aliphatic or aromatic nature; (iii) the points of zero charge (PZC) of the photocatalysts; (iv) their relative rate constants for photoelectron-hole recombination (k r ) determined by femtosecond pump-probe diffuse reflectance spectroscopy.

Silver nanoclusters embedded in glass matrices have been obtained by the combined use of ion exchange and subsequent ion implantation. XRD and UV-visible spectro-photometric analysis have con"rmed the formation of Ag nano-clusters in the ion-irradiated samples. Temperature-dependent resistivity measurements of the irradiated samples have been found to follow (¹)Jexp((¹ /¹) in the temperature range of 80}280 K. The observed behaviour of (¹) is consistent with charge transport due to hopping between isolated, conducting islands. The separation distance between the conducting islands has been found to be a function of #uence.

Plasma immersion ion implantation (PIII) is a cluster compatible doping and processing tool offering many inherent advantages over conventional beamline ion implantation. When first introduced in the late 1980s, the technique was primarily used to enhance the surface mechanical properties of metals. Recently, a substantial amount of research activities have focused on microelectronics and have led to a number of very interesting applications, such as the formation of shallow junction, synthesis of silicon-on-insulator, large area implantation, trench doping, conformal deposition, and so on. In this paper, we will review the principles of PIII, the dynamic sheath model for various kinds of plasma, reactor designs, recent applications in the area of microelectronics, as well as the future of PIII pertaining to semiconductor materials and processing.

We have obtained room-temperature electroluminescence (EL) at -1.54 pm from Er and 0 co-doped crystalline p-n Si diodes fabricated by ion implantation, under both forward and reverse bias conditions. Under forward bias, the EL intensity decreases by a factor of -15 on going from 110 to 300 K, where a weak peak is still visible. In contrast, we report the first sharp luminescence peak obtained under reverse bias conditions in the breakdown regime. In this case the EL intensity decreases only by a factor of 4 on going from 110 to 300 K and the room-temperature yield is more than one order of magnitude higher than under forward bias. The data suggest that Er excitation occurs through electron-hole mediated processes under forward bias and through impact excitation under reverse bias.

Staphylococcus epidermidis is the primary cause of medical device-related infections due to its adhesion and biofilm forming abilities on biomaterial surfaces. For this reason development of new materials and surfaces to prevent bacterial adhesion is inevitable. In this study, the adhesion of biofilm forming S. epidermidis strain YT-169a on nitrogen (N) ion implanted as well as on as-polished CoCrMo alloy materials were investigated. A medical grade CoCrMo alloy was ion implanted with 60 keV N ions to a high dose of 1.9 Â 10 18 ions/cm 2 at substrate temperatures of 200 and 4008C. The near-surface implanted layer crystal structures, implanted layer thicknesses, and roughnesses were characterized by XRD, SEM and AFM. The number of adherent bacteria on the surfaces of N implanted specimens was found to be 191 Â 10 6 CFU/cm 2 for the 2008C and 70 Â 10 6 CFU/cm 2 for the 4008C specimens compared to the as-polished specimen (3 Â 10 6 CFU/cm 2). The adhesion test results showed that S. epidermidis strain YT-169a adhere much more efficiently to the N implanted surfaces than to the as-polished CoCrMo alloy surface. This was attributed mainly to the rougher surfaces associated with the N implanted specimens in comparison with the relatively smooth surface of the as-polished specimen. 2006 Wiley

As one of most efficient techniques for material-property modification, ion implantation has shown its unique ability for alteration of surface refractive index of a large number of optical materials, forming waveguide structures. The induced refractive index changes are materials related, and closely dependent on the species, energies and doses of the implanted ions. This paper reviews the results of recent research on the fabrication, investigation and applications of the ion-implanted optical waveguides in various optical materials, including crystals and non-crystalline glasses. As will be summarized, ion implantation offers a nearly universal solution for the waveguide fabrication in most existing optical materials to date, which opens up new possibilities of attractive optical applications.

Field emission properties of tetrahedral amorphous carbon films prepared by filtered cathodic vacuum arc technique have been compared with different surface morphologies. With fewer cycles of conditioning, field emission from relatively rough granular ta-C films on nickel-coated silicon substrates was routinely improved, due to a local field enhancement resulting from both a 'protrusion-on-protrusion' geometry and a relatively high sp 2 content in the film. A 2-MeV ion implantation machine was also employed to intentionally produce local graphitic channels in smooth ta-C films with a high fraction of sp 3 content on bare silicon. A relatively low threshold field was obtained from the ta-C film implanted at a dose of 10 12 cm y2 , which still remained an extremely smooth surface. However, for the highly graphitic sample implanted with a higher dose of over 4 = 10 13 cm y2 , no electron field emission was observed, even under a very high electric field of 40 V m y1 . Therefore, a suitable sp 2 content in an sp 3 matrix, resulting in graphitic conductive channels in amorphous carbon films to produce a local field enhancement, may be the main factor in obtaining low threshold fields. Furthermore, protrusive structures could further increase the field enhancement factor, due to a 'protrusion-on-protrusion' geometry. ᮊ

A review of mainly the past two years is undertaken of the industrial applications of pulsed power. Repetitively operated pulsed power generators with a moderate peak power have been developed for industrial applications. These generators are reliable and have low maintenance. Development of the pulsed power generators helps promote industrial applications of pulsed power for such things as food processing, medical treatment, water treatment, exhaust gas treatment, ozone generation, engine ignition, ion implantation and others. Here, industrial applications of pulsed power are classified by application for biological effects, for pulsed streamer discharges in gases, for pulsed discharges in liquid or liquidmixture, and for material processing.

Chemical stability, mechanical behaviour and biocompatibility in body fluids and tissues are the basic requirements for successful application of implant materials in bone fractures and replacements. Corrosion is one of the major processes affecting the life and service of orthopaedic devices made of metals and alloys used as implants in the body. Among the metals and alloys known, stainless steels (SS), Co-Cr alloys and titanium and its alloys are the most widely used for the making of biodevices for extended life in human body. Incidences of failure of stainless steel implant devices reveal the occurrence of significant localised corroding viz., pitting and crevice corrosion. Titanium forms a stable TiO 2 film which can release titanium particles under wear into the body environment. To reduce corrosion and achieve better biocompatibility, bulk alloying of stainless steels with titanium and nitrogen, surface alloying by ion implantation of stainless steels and titanium and its alloys, and surface modification of stainless steel with bioceramic coatings are considered potential methods for improving the performance of orthopaedic devices. This review discusses these issues in depth and examines emerging directions.

We have demonstrated symmetrically high levels of electrical activation of both p-and n-type dopants in germanium. Rapid thermal annealing of various commonly implanted dopant species were performed in the temperature range of 600-850°C in germanium substrates. Diffusion studies were also carried out by using different anneal times and temperatures. T-SUPREM™ simulations were used to fit the experimental profiles and to extract the diffusion coefficient of various dopants.

Theoretical approaches to channeling and blocking of 6.2. The formation and annealing of In-vacancy comcharged particles from nuclear decay 135 plexes in Cu 161 4.1. Theoretical models for electron channeling 138 6.3. He decorated impurity-vacancy complexes in Cu 164 4.2. Model calculations for channeling of electrons with 7. Impurity lattice location and defect annealing in ion imenergies below 1 MeV 145 planted semiconductors 167 4.3. Channeling and blocking of positrons emitted from 7.1. Lattice location of ion implanted In and Cd impurities radioactive probe atoms 149 in Si 168 5. Characteristic features of electron emission channeling 151 7.2. Impurity lattice sites and defect annealing in ion im-5.1. Displacement of probe atoms from substitutional sites 151 planted GaAs 169 5.2. Qualitative interpretation of emission channeling 7.3. Probing of mobile vacancies in GaAs with Li imwithin the classical continuum model 152 purities 172 5.3. Dechanneling of electrons 153 8. Summary and outlook 174 5.4. Temperature dependence of electron channeling 156 References 178

Silicon nanowires will find applications in nanoscale electronics and optoelectronics both as active and passive components. Here, we demonstrate a low-temperature vapor-liquid-solid synthesis method that uses liquid-metal solvents with low solubility for silicon and other elemental semiconductor materials. This method eliminates the usual requirement of quantum-sized droplets in order to obtain quantum-scale one-dimensional structures. Specifically, we synthesized silicon nanowires with uniform diameters distributed around 6 nm using gallium as the molten solvent, at temperatures less than 400°C in hydrogen plasma. The potential exists for bulk synthesis of silicon nanowires at temperatures significantly lower than 400°C. Gallium forms a eutectic with silicon near room temperature and offers a wide temperature range for bulk synthesis of nanowires. These properties are important for creating monodispersed one-dimensional structures capable of yielding sharp hetero-or homointerfaces.

A B S T R A C T The energy demand is ever increasing on aspect of primary and secondary energy sources to fulfill the energy requirement in this century. High energy supply is required especially in the developing countries to sustain the lifestyle due to the growth in the world's population and techno-economic city. In fact, the sources of fossil fuel-based energy are limited and the use of fossil fuels can lead to the environmental pollution problem. Accordingly, the combustion of fossil fuels sources will give rise to the global warming issue, i.e., the greenhouse effect of carbon dioxide resulting in erratic weather patterns, such as floods, draughts, etc. In the last two decades, solar photovoltaic cells have been used as the alternatives to generate renewable, sustainable and green energy. High dye absorption rates, efficient charge separation of exciton, and free charge carrier formation as well as large area production at low costs contribute to the emerging photovoltaic technologies. Generally, the materials involved in photoanode section (acting as the platform for the electron collection) are the main key to produce high-efficiency photovoltaic cells. Currently, multijunction based solar panels showed the highest performance of 40% efficiency as compared to that of the conventional Si based solar panels with 22–27% efficiency. Apart of that, DSSCs sensitized by the silyl-anchor and carboxy-anchor dyes have attained the highest efficiency of 14%. In recent years, the metal doping or binary oxide photo-catalyst systems, particularly gra-phene-TiO 2 nanocomposites, have attracted much attention due to their extraordinary characteristics, i.e., (i) photocatalyst activity enhancement, and (ii) accelerated electron mobility to reduce the charge recombination. The high efficiency of the graphene-TiO 2 nanocomposites in DSSCs' reaction basically requires a suitable architecture that minimizes electron loss during excitation state and maximizes photon absorption. In order to further improve the immigration of photo-induced charge carriers during excitation state, considerable efforts have to be exerted to further improve the charge mobility and maximize the dye loading. It has also been reported that the properties of graphene-TiO 2 nanocomposites primarily depend on the nature of the preparation method, and the role of optimum dopants content incorporated into the graphene photoanode to improve the dye molecules loading and minimize the charge recombination. Therefore, we review recent achievements for different nanoarchitecture of TiO 2 , as well as graphene-TiO 2 composite nanostructured based photoanode in DSSCs performance with future prospects and challenges. Indeed, graphene-TiO 2 composite photoanode has proven to be of great interest for use in DSSCs.

We investigate the effect of surface termination on the charge state of nitrogen vacancy centers, which have been ion-implanted few nanometers below the surface of diamond. We find that, when changing the surface termination from oxygen to hydrogen, previously stable NV − centers convert into NV 0 and, subsequently, into an unknown non-fluorescent state. This effect is found to depend strongly on the implantation dose. Simulations of the electronic band structure confirm the dissappearance of NV − in the vicinity of the hydrogen-terminated surface. The band bending, which induces a p-type surface conductive layer leads to a depletion of electrons in the nitrogenvacancies close to the surface. Therefore, hydrogen surface termination provides a chemical way for the control of the charge state of nitrogen-vacancy centers in diamond. Furthermore, it opens the way to an electrostatic control of the charge state with the use of an external gate electrode.

Mesoporous TiO 2 has attracted great attention as a promising Li insertion electrode material with improved cycling life, rate capability, and high power density. Up to date, mesoporous anatase TiO 2 has been investigated for Li insertion. Recent studies have shown that nanosized rutile could be an excellent candidate for anode materials for higher Li insertion capacity and improved stability. However, synthesis of highly crystalline mesoporous rutile has met with limited success so far. There has been no report on Li insertion of mesoporous rutile TiO 2 . In this paper, we report a new low-temperature solution growth of TiO 2 nanocrystals within an anionic surfactant matrix to produce highly crystalline mesoporous rutile and investigate Li insertion properties of the mesoporous crystalline rutile. X-ray diffraction (XRD) patterns and N 2 sorption isotherms reveal that mesoporous structure in the highly crystalline mesoporous TiO 2 directly results from the anionic surfactant templating effects with high surface area (245-300 m 2 /g) and tunable mesopore diameter ranging from 2.2 to 3.8 nm after calcination. Transmission electron microscopy (TEM) measurements show that framework of the highly crystalline mesoporous TiO 2 are composed of aligned rutile nanorod building blocks grown along [001] direction. The new mesoporous crystalline rutile can accommodate more than 0.7 Li (Li 0.7 TiO 2 , 235 mA h g -1 ) during the first discharge at a C/5 rate between 1 and 3 V versus Li + /Li, with a reversible capacity of 0.55 Li (Li 0.55 TiO 2 , 185 mA h g -1 ). The mesoporous crystalline rutile shows excellent capacity retention with less than 10% capacity loss after more than 100 cycles. XRD and TEM characterization on the electrochemically lithiated sample show that the rutile nanorods were transformed into cubic rocksalt LiTiO 2 nanorods, but the mesostructures remained stable after the phase transformation and cycling. Furthermore, the crystalline mesoporous rutile may also have good potential for other applications such as stable catalyst supports.

Above room temperature ferromagnetic behavior is achieved in Si through Mn ion implantation. Threehundred-keV Mn + ions were implanted to 0.1% and 0.8% peak atomic concentrations, yielding a saturation magnetization of 0.3 emu/ g at 300 K for the highest concentration as measured using a SQUID magnetometer. The saturation magnetization increased by ϳ2ϫ after annealing at 800°C for 5 min. The Curie temperature for all samples was found to be greater than 400 K. A significant difference in the temperature-dependent remnant magnetization between the implanted p-type and n-type Si is observed, giving strong evidence that a Si-based diluted magnetic semiconductor can be achieved.

Double gate devices based upon the FinFET architecture are fabricated, with gate lengths as small as 30 nm. Particular attention is given to minimizing the parasitic series resistance. Angled extension implants and selective silicon epitaxy are investigated as methods for minimizing parasitic resistance in FinFETs. Using these two techniques high performance devices are fabricated with on-currents comparable to fully optimized bulk silicon technologies. The influence of fin thickness on device resistance and short channel effects is discussed in detail. Devices are fabricated with fins oriented in the 100 and 100 directions showing different transport properties.

During the last two decades, the industry (including scientists) has focused on diamond-like carbon (DLC) coating because of its wide range of application in various fields. This material has numerous applications in mechanical, electrical, tribological, biomedical, and optical fields. Severe friction and wear in some machine parts consumes high amount of energy, which makes the process energy inefficient. Thus, DLC coating can be an effective means to lower the friction and wear rate. Some important process variables that affect the tribological characteristics of DLC coating are adhesion promoter intermediate layer, substrate surface roughness, hydrogen incorporation or hydrogen non involvement, and coating deposition parameters (e.g., bias voltage, etching, current, precursor gas, time, and substrate temperature). Working condition of DLC-coated parts also affects the tribological characteristics, such as temperature, sliding speed and load, relative humidity, counter surface, and lubrication media (DLC additive interaction). Different types of lubricated oils and additives are used in engine parts to minimize friction and wear. DLC can be coated to the respective engine parts; however, DLC does not behave accordingly after coating because of lubricant oil and additive interaction with DLC. Some additive interacts positively and some behave negatively because of the tribochemical reactions between DLC coating and additives. Numerous conflicting views have been presented by several researchers regarding this coating additive interaction, resulting in unclear determination of true mechanism of such interaction. However, lubricant additive has been established to be more inert to DLC coating compared with uncoated metal surface because the additive is fabricated in such a way that it can react with metal surfaces. In this article, the tribological characteristics of different types of DLC coating in dry and lubricated conditions will be presented, and their behavior will be discussed in relation to working condition and processing parameters.

Thin films grown by Al 2 O 3 atomic layer deposition ͑ALD͒ and SiN plasma-enhanced chemical vapor deposition ͑PECVD͒ have been tested as gas diffusion barriers either individually or as bilayers on polymer substrates. Single films of Al 2 O 3 ALD with thicknesses of Ն10 nm had a water vapor transmission rate ͑WVTR͒ of Յ5 ϫ 10 −5 g / m 2 day at 38°C / 85% relative humidity ͑RH͒, as measured by the Ca test. This WVTR value was limited by H 2 O permeability through the epoxy seal, as determined by the Ca test for the glass lid control. In comparison, SiN PECVD films with a thickness of 100 nm had a WVTR of ϳ7 ϫ 10 −3 g / m 2 day at 38°C / 85% RH. Significant improvements resulted when the SiN PECVD film was coated with an Al 2 O 3 ALD film. An Al 2 O 3 ALD film with a thickness of only 5 nm on a SiN PECVD film with a thickness of 100 nm reduced the WVTR from ϳ7 ϫ 10 −3 to Յ5 ϫ 10 −5 g / m 2 day at 38°C / 85% RH. The reduction in the permeability for Al 2 O 3 ALD on the SiN PECVD films was attributed to either Al 2 O 3 ALD sealing defects in the SiN PECVD film or improved nucleation of Al 2 O 3 ALD on SiN.

LLC resonant converter with significant resonant inductance is proposed for designing an adjustable wide-range regulated voltage source. Large resonant inductance increases output voltage adjustment range and conversion efficiency, particularly at light loads. Soft switching is achieved for all power devices under all operating conditions by choosing the dead time and maximum switching frequency properly and operating in the converter's inductive region. Using a power-factor-correction (PFC) converter reduces the resonant converter's output voltage dependence to the variations of the main ac input voltage. Thus, the compensation of the load variations and the wide-range adjustment of the regulated output voltage can be achieved by using small switching frequency variations. The proposed method has been used to implement an adjustable wide-range voltage source (35-165 V dc), as an ion implanter arc power supply. An almost flat efficiency curve with maximum value of 94% has been achieved for the converter. Its output current can change from no load to 3 A dc. Index Terms-Dead time, LLC resonant converter, wide adjustable range, zero-current switching (ZCS), zero-voltage switching (ZVS).

64 keV Ni ion implantation was performed at room temperature up to a dose of 1ϫ10 17 cm Ϫ2 in ␣-Al 2 O 3 single crystals. The charge states, structure, and optical properties of metallic embedded Ni nanoparticles were studied by using x-ray photoelectron spectroscopy ͑XPS͒, transmission electron microscopy, and optical spectroscopy, respectively. XPS analysis showed that implanted Ni ions are mainly in charge state of metallic Ni 0 . Nanoparticles distributed from the surface to 30 nm below the surface were observed in a high-angle annular dark-field image. The size of nanoparticles ranges from 1 to 5 nm in diameter. A high-resolution electron microscopy image indicated the Ni-implanted area had been entirely amorphized. A new broad absorption band centered at 400 nm appeared in the optical absorption spectrum of the as-implanted crystal, due to surface plasma resonance of Ni nanoparticles. We did not find any emission band in the as-implanted sample under a Xe lamp excitation wavelength of 250-430 nm in a spectrophotometer.

LLC resonant converter is one of the most suitable circuit topologies that have been introduced for designing constant output voltage switched-mode power supplies. In this paper, a design procedure is introduced for using this converter as a wide output range voltage source. Unlike constant output voltage applications which need small converter inductance ratio and narrow switching frequency variations, for wide output range applications, large values of these parameters are needed simultaneously and should be optimized. Instead of minimizing the components stresses, leading to a great value of the inductance ratio, proper choice of the converter parameters resulting in a smaller inductance ratio has been done. Maximum value of the capacitor in parallel with the power MOSFETs drain-sources has been derived to realize the zero voltage switching operation in the converter inductive region. Soft switching is achieved for all power devices under all operating conditions. A prototype of the converter has been tested for different regulated output voltages (35-165 V d c) under different loads (0-3 A d c) and input voltages (320-370 V d c) for using an ion implanter arc power supply, with maximum efficiency value of 94.7%. Experimental results confirm the high performance of the wide output range LLC resonant converter even under the worst case conditions. Index Terms-LLC resonant converter, switched-mode power supply (SMPS), wide output range, zero current switching (ZCS), zero voltage switching (ZVS). NOMENCLATURE a, n Converter inductance ratio and transformer turns ratio. I in N and I in max N Normalized ac input current and its maximum value. I out and I out max Output dc current and its maximum value. I DSM 1 and I D MOSFET drain-source and diode currents. k z Converter's input impedance ratio. V in , V in min , DC input voltage and its maximum and minimum values. and V in max V in N , V in min N , Normalized dc input voltage and its maximum and minimum values. and V in max N

Nitrogen ( 15 N) and carbon ( 12 C) ion implantations with implant energy of 100 keV for different doses were performed on nanosized diamond (ND) particles. Magnetic measurements on the doped ND show ferromagnetic hysteresis behavior at room temperature. The saturation magnetization (M s ) in the case of 15 N implanted samples was found to be higher compared to the 12 C implanted samples for dose sizes greater than 10 14 cm ÿ2 . The role of structural modification or defects along with the carbon-nitrogen (C-N) bonding states for the observed enhanced ferromagnetic ordering in 15 N doped samples is explained on the basis of x-ray photoelectron spectroscopy measurements.

A method for the fabrication of luminescent Si nanoclusters in an amorphous SiO 2 matrix by ion implantation is reported. We have measured the dose ͑concentration of excess Si atoms͒ and annealing time dependence of the photoluminescence of Si nanoclusters in SiO 2 layers at room temperature. The samples were fabricated by ion implantation and subsequent annealing. After annealing, a photoluminescence band below 1.7 eV has been observed. The peak energy of the photoluminescence is found to be almost independent of annealing time, while the intensity of the luminescence increases as the annealing time increases. Moreover, we found that the peak energy of the luminescence is strongly affected by the dose of implanted Si ions, especially in the high-dose range. We also show direct evidence of widening of the band-gap energy of Si particles of a few nanometers in size by employing photoacoustic spectroscopy. These results indicate that the photons are absorbed by Si nanoclusters, for which the band-gap energy is modified by the quantum confinement effects, and the emission is not simply due to direct electron-hole recombination inside Si nanoclusters, but is related to defects probably at the interface between the Si nanoclusters and SiO 2 , for which the energy state is affected by cluster-cluster interactions.

Diamond has attracted great interest as a quantum technology platform thanks to its optically active nitrogen vacancy (NV) center. The NV's ground state spin can be read out optically, exhibiting long spin coherence times of 1 ms even at ambient temperatures. In addition, the energy levels of the NV are sensitive to external fields. These properties make NVs attractive as a scalable platform for efficient nanoscale resolution sensing based on electron spins and for quantum information systems. Diamond photonics enhance optical interactions with NVs, beneficial for both quantum sensing and information. Diamond is also compelling for microfluidic applications due to its outstanding biocompatibility, with sensing functionality provided by NVs. However, it remains a significant challenge to fabricate photonics, NVs, and microfluidics in diamond. In this Progress Report, an overview is provided of ion irradiation and femtosecond laser writing, two promising fabrication methods for diamond-based quantum technological devices. The unique capabilities of both techniques are described, and the most important fabrication results of color center, optical waveguide, and microfluidics in diamond are reported, with an emphasis on integrated devices aiming toward high performance quantum sensors and quantum information systems of tomorrow.

Nitrogen and sulfur co-doping has been achieved in the commercial TiO2 nanoparticles of anatase TKP 102 (Tayca) by grinding it with thiourea and calcinating at 400 °C. The successful substitutional N-doping and cationic/anionic S-doping were validated by XPS measurements. Diffuse reflectance spectroscopy (DRS) showed a marked broadening of the absorption spectrum of the doped material towards the visible range.Phenol and dichloroacetate (DCA) oxidation and Escherichia coli inactivation were achieved under UV illumination using the N, S co-doped TiO2 powders. Electron spin resonance (ESR) spin-trapping experiments showed that under UV light irradiation, the Moreover, under visible light (400–500 nm) illumination of N, S co-doped TiO2 a complete inactivation of E. coli bacteria was observed. In contrast, under such conditions, phenol was only partially degraded, whereas DCA was not at all affected. ESR experiments performed with N, S co-doped TiO2 powders illuminated with visible light and in the presence of singlet oxygen (1O2) quencher, TMP-OH, showed the formation of 1O2. This suggests that superoxide radical (

Titanium and its alloys are widely used as implant materials. Their integration in the bone is in general very good without fibrous interface layer. However, titanium and its alloys have certain limitations. Metal ions are released from the implant alloy and have been detected in tissues close to titanium implants. The release of these elements, even in small amounts, may cause local irritation of the tissues surrounding the implant. Cell and tissue responses are affected not only by the chemical properties of the implant surface, but also by the surface topography or roughness of the implants. To overcome the problem of ion release and to improve the biological, chemical, and mechanical properties, many surface treatment techniques are used. Any surface treatment that would elicit favorable response from tissues can be applied to enhance the usefulness of the implants. In view of this, the current review describes surface modification of titanium and titanium alloys by ion beam implantation.

We review the recent progress in the development of photonic applications based on the organic crystal 4-N, Ndimethylamino-4 -N -methyl-stilbazolium tosylate (DAST). DAST is an organic salt with an extremely high nonlinear optical susceptibility χ (2 ) (-2ω, ω, ω) = 580 ± 30 pm/V at 1.54 µm, a high electrooptic figure of merit n 3 r = 455 ± 80 pm/V at 1.54 µm, as well as a low dielectric constant = 5.2. DAST is, therefore, very attractive for high-speed optical modulators and field detectors, as well as for frequency conversion and the generation of terahertz waves. Several techniques to microscopically structure this material have been developed recently; including modified photolithography, photobleaching, femtosecond laser ablation, graphoepitaxial growth, ion implantation, and direct electron-beam structuring, which open new perspectives of using this exceptional material for high-speed very-large-scale integrated photonics.

Silicon nanocrystals with diameters ranging from Ϸ2 to 5.5 nm were formed by Si ion implantation into SiO 2 followed by annealing. After passivation with deuterium, the photoluminescence ͑PL͒ spectrum at 12 K peaks at 1.60 eV and has a full width at half maximum of 0.28 eV. The emission is attributed to the recombination of quantum-confined excitons in the nanocrystals. The temperature dependence of the PL intensity and decay rate at several energies between 1.4 and 1.9 eV was determined between 12 and 300 K. The temperature dependence of the radiative decay rate was determined, and is in good agreement with a model that takes into account the energy splitting between the excitonic singlet and triplet levels due to the electron-hole exchange interaction. The exchange energy splitting increases from 8.4 meV for large nanocrystals ͑Ϸ5.5 nm͒ to 16.5 meV for small nanocrystals ͑Ϸ2 nm͒. For all nanocrystal sizes, the radiative rate from the singlet state is 300-800 times larger than the radiative rate from the triplet state.

An overview of the rapidly developing field of modification of engineering polymers by plasma based ion implantation (PBII) and plasma based ion implantation and deposition (PBII&D) is presented. Furthermore, the applicability and usefulness of the approach of "design of experiments" is demonstrated by the nitrogen PBII treatments of polyamide 6 (PA) and poly(bisphenol A carbonate) (PC). Alterations in surface chemical composition and bonding were studied by XPS. Modifications in surface mechanical and tribological properties were followed by dynamic depth-sensitive nanoindentation and multiple nanoscratch measurements. Changes in wettability, surface energy and its components were evaluated by contact angle studies. Alterations in surface electrical resistance were also determined. Surface compositional changes reflected a relative decrease in the C-content and increase in the N-content for both polymers, while alterations in the peak shapes suggested degradation of the amide group with the formation of imine, protonated amine and urethane-like moieties for PA, and degradation of surface carbonate groups with the formation of imine, tertiary amine and amide-like groups for PC. The hydrophilicity of the surface increased and the surface electrical resistance decreased significantly for both polymers. The volume loss, obtained by the multi-pass scratch test, decreased from the original value expressed as V 0 = 100%, down to V = 11% and 59% for PA and PC, respectively. For PA the incorporation of some N had a favorable effect on the resistance to abrasive wear, but an excessive amount of N decreased this effect. Similarly, for PC a significant increase of the wear resistance could not be reached by the mere increase of the total N-content, but the surface concentration of tertiary amine type N should be maximized. The latter showed positive correlations with the fluence and the fluence rate applied.

Free carrier absorption in heavily doped layers reduces the useful photon flux in the photoconductive region of extrinsic Si infrared detectors. A simple theory is developed which predicts the transmissivity of such layers as a function of their sheet resistance and the wavelength of the radiation. Experimental data over the 2.5-20 µm wavelength and 5-500 Ω/square sheet resistance range are given for both diffused and ion-implanted layers and also for polysilicon gases. The temperature dependence of both transmissivity and sheet resistance is investigated from 20 to 300 K.

Rutherford backscattering spectrometry and related techniques have long been used to determine the elemental depth profiles in films a few nms to a few microns thick. However, although obtaining spectra is very easy, solving the inverse problem of extracting the depth profiles from the spectra is not possible analytically except for special cases. It is because these special cases include important classes of samples, and because skilled analysts are adept at extracting useful qualitative information from the data, that ion beam analysis is still an important technique.

This paper presents the design and development of a silicon-based three-axial force sensor to be used in a flexible smart interface for biomechanical measurements. Normal and shear forces are detected by combining responses from four piezoresistors obtained by ion implantation in a high aspect-ratio cross-shape flexible element equipped with a 525 m high silicon mesa. The mesa is obtained by a subtractive dry etching process of the whole handle layer of an SOI wafer. Piezoresistor size ranges between 6 and 10 m in width, and between 30 and 50 m in length. The sensor configuration follows a hybrid integration approach for interconnection and for future electronic circuitry system integration. The sensor ability to measure both normal and shear forces with high linearity ( ∼ =99%) and low hysteresis is demonstrated by means of tests performed by applying forces from 0 to 2 N. In this paper the packaging design is also presented and materials for flexible sensor array preliminary assembly are described.

The mechanisms for silicon ͑Si͒ defect and nanocrystal related white and near-infrared electroluminescences ͑ELs͒ of Si-rich SiO 2 films synthesized by Si-ion implantation and plasma-enhanced chemical-vapor deposition ͑PECVD͒ are investigated. The strong photoluminescence ͑PL͒ of Si-ion-implanted SiO 2 ͑SiO 2 :Si + ͒ at 415-455 nm contributed by weak-oxygen bond and neutral oxygen vacancy defects is observed after 1100°C annealing for 180 min. The white-light EL of a reverse-biased SiO 2 :Si + metal-oxide-semiconductor ͑MOS͒ diode with a turn-on voltage of 3.3 V originates from the minority-carrier tunneling and recombination in the defect states of SiO 2 :Si + , which exhibits maximum EL power of 120 nW at bias of 15 V with a power-current slope of 2.2 W / A. The precipitation of nanocrystallite silicon ͑nc-Si͒ in SiO 2 :Si + is less pronounced due to relatively small excess Si density. In contrast, the 4-nm nc-Si contributed to PL and EL at about 760 nm is precipitated in the PECVD-grown Si-rich SiO x film after annealing at 1100°C for 30 min. The indium-tin-oxide/Si-rich SiO x / p -Si/ Al metal oxide semiconductor ͑MOS͒ diode is highly resistive with turn-on voltage and power-current ͑P-I͒ slope of 86 V and 0.7 mW/ A, respectively. The decomposed EL peaks at 625 and 768 nm are contributed by the bias-dependent cold-carrier tunneling between the excited states in adjacent nc-Si quantum dots.

We have studied the effect of erbium-impurity interactions on the 1.54 pm luminescence of EJ?' in crystalline Si. Float-zone and Czochralski-grown (100) oriented Si wafers were implanted with Er at a total dose of -1 X 10'5/cm2. Some samples were also coimplanted with 0, C, and F to realize uniform concentrations (up to 102'/cm3) of these impurities in the Er-doped region. Samples were analyzed by photoluminescence spectroscopy (PL) and electron paramagnetic resonance (EPR). Deep-level transient spectroscopy (DLTS) was also performed on p-n diodes implanted with Er at a dose of 6XlO"/cmz and codoped with impurities at a constant concentration of 1X101s/cm3. It was found that impurity codoping reduces the temperature quenching of the PL yield and that this reduction is more marked when the impurity concentration is increased. An EPR spectrum of sharp, anisotropic, lines is obtained for the sample codoped with 102' O/cm3 but no clear EPR signal is observed without this codoping. The spectrum for the magnetic field B parallel to the [ 1001 direction is similar to that expected for Ersf in an approximately octahedral crystal field. DLTS analyses confirmed the formation of new Ers' sites in the presence of the codoping impurities. In particular, a reduction in the density of the deepest levels has been observed and an impurity+Er-related level at -0.15 eV below the conduction band has been identified. This level is present in Er+O-, ErfF-, and ErfC-doped Si samples while it is not observed in samples solely doped with Er or with the codoping impurity onIy. We suggest that this new level causes efficient excitation of Er through the recombination of e-h pairs bound to this level. Temperature quenching is ascribed to the thermalization of bound electrons to the conduction band. We show that the attainment of well-defined impurity-related luminescent Er centers is responsible for both the luminescence enhancement at low temperatures and for the reduction of the temperature quenching of the * huninescence. A quantitative model for the excitation and deexcitation processes of Er in Si is also proposed and shows good agreement with the experimental results. 0 1995 American Institute of Physics.

A suspended nanogap formed by field-induced atomically sharp tips Appl. Phys. Lett. 101, 183106 (2012) Generalized interface models for transport phenomena: Unusual scale effects in composite nanomaterials J. Appl. Phys. 112, 084306 (2012) Thermoelectric properties of highly doped n-type polysilicon inverse opals J. Appl. Phys. 112, 073719 Enhanced thermoelectric performance through energy-filtering effects in nanocomposites dispersed with metallic particles Appl.

The integrated circuit (IC) industry has followed a steady path of shrinking device geometries for more than 30 years. It is widely believed that this process will continue for at least another ten years. However, there are increasingly difficult materials and technology problems to be solved over the next decade if this is to actually occur and, beyond ten years, there is great uncertainty about the ability to continue scaling metal-oxide-semiconductor field-effect transistor (MOSFET) structures. This paper describes some of the most challenging materials and process issues to be faced in the future and, where possible solutions are known, describes these potential solutions. The paper is written with the underlying assumption that the basic metal-oxide-semiconductor (MOS) transistor will remain the dominant switching device used in ICs and it further assumes that silicon will remain the dominant substrate material.

We present an erbium-doped microlaser on silicon operating at a wavelength of 1.5 m that operates at a launched pump threshold as low as 4.5 W. The 40 m diameter toroidal microresonator is made using a combination of erbium ion implantation, photolithography, wet and dry etching, and laser annealing, using a thermally grown SiO 2 film on a Si substrate as a starting material. The microlaser, doped with an average Er concentration of 2ϫ10 19 cm Ϫ3 , is pumped at 1480 nm using an evanescently coupled tapered optical fiber. Cavity quality factors as high as 3.9ϫ10 7 are achieved, corresponding to a modal loss of 0.007 dB/cm, and single-mode lasing is observed.