Electron Beam Writing

Single donors in semiconductor nanostructures represent a key element to develop spin related quantum functionalities in atomic scale devices. Quantum transport through a single Arsenic donor in the channel of a Silicon nano-field effect transistor under microwave irradiation is investigated. The device is characterized at mK temperatures in the regime of Coulomb-blockade. Photon assisted tunneling and microwave induced electron pumping regimes are revealed respectively at low and high microwave power. At sufficiently high power, the microwave irradiation induces tunneling through the first excited energy level of the D 0 energy of the donor. Such microwave assisted transport at zero bias enhances the resolution in the spectroscopy of the energy levels of the donor.

The electron-beam response of new chemically amplified positive multi-component ARCH-resist family (ARCH and ARCH2) and the suitability of pattern transfer through single layer has been evaluated. The electron-beam lithographic parameters for thicker layers (1-2~tm) of these resists and the optimization possibilities of the exposure and etching conditions were investigated as well. Under fixed resist-handling processes, both resists exhibit high sensitivity (< 101aC/cm0 and an enormous high contrast. The study includes the effects of resist-process variations on the global 3-D resist-relief structure. Vertical side-walls of the resist profile is a necessary condition for a successful deep-, and a good CD-controlled anizotropical pattern transfer with high aspect ratio of structures into the substrate.

The effect of post exposure bake and softbake conditions on the sensitivity of AZPN114 has been investigated experimentally. A bilayer system for undercut structures has been achieved using two layers of AZPN114 with different softbake temperatures. A single layer of AZPN1 i4 has also been used to produce undercut and tailored resist profffles by two different multiple exposure strategies at different beam energies.

The effect of post exposure bake and softbake conditions on the sensitivity of AZPN114 has been investigated experimentally. A bilayer system for undercut structures has been achieved using two layers of AZPN114 with different softbake temperatures. A single layer of AZPN1 i4 has also been used to produce undercut and tailored resist profffles by two different multiple exposure strategies at different beam energies.

InSb is a III-V narrow-gap semiconductor with properties such as low effective mass, high mobility, and strong spin-orbit coupling making it an ideal material for applications such as spintronics [1] mid-infrared photonics [2], and nanoelectronics [3]. InSb quantum wells can be made by growing an InSb/InAlSb structure on a Ga substrate using molecular beam epitaxy [4]. However, it is notoriously difficult to fabricate nanodevices from InSb/InAlSb quantum wells due to factors such as its low thermal budget [5] and the production of non-volatile by-products in conventional etching processes, leading to unwanted deposition of material onto the material surface [6]. Current wet and dry etching techniques take a long time and require expensive lithography masks to make new devices, slowing the development of optimised nanodevices.

We investigate focused ion beam (FIB) lithography as a ˜rapid prototyping" fabrication technique to create semiconductor nanodevices from InSb quantum wells. FIB methods have the advantage of being relatively quick and ˜masklessâ", making them ideal for use in the research environment as new iterations of device design can be made quickly and different etching chemistries and electrical properties can be tested in-situ [7]. A variety of Xe plasma FIB parameters were tested to optimise the feature resolution and etching quality of milled trenches at low temperatures. The XeF2 gas-assisted etching process was also studied as an alternative to the Cl2 chemistry that is typically employed for dry etching of InSb. Cross-sections and profiles of the trenches indicate that the XeF2 etch yields superior trench smoothness and mills material from the surface at a much higher rate. This method was also less prone to deposition of unwanted material onto the surface of the sample. This high-resolution fabrication method can be used for the rapid development and optimisation of individual nanoscale devices before mass production.

In this paper, a process for 200 lm high-aspectratio micro-optical (HARM) structures fabricated by deep X-ray lithography (DXRL) of polymethylislesuioane-based spin-on glass (SOG) thick films is presented. The SOG material used in the whole procedures is polymethylsilsesquioxane (GR650), which is a kind of sol-gel derived material and can be cured at a reasonable low temperature (75°C). A technique to cast thick GR650 films was established in the overall process. After consolidation, the GR650 thick films were machined to reach 200 lm uniformly. Then, as negative resists, the GR650 thick films were patterned directly by DXRL. X-ray irradiated regions can be selectively retained with high structural resolution by development in an organic solvent, such as methanol. Parameter screening was done to find minimum and maximum doses needed for patterning/cross-linking, to vary development time, and to explore different film thickness. The whole process is a novel of technique to create HARM structures based on SOG materials without using molds. This technique can be extended to considerably larger structural heights. Surface and bulk compositions of the irradiated films were measured by XPS and Fourier transform infrared spectroscopy. Surface quality by roughness testing system (WYKO RST) was investigated to fabricate the microstructure with a high-accuracy surface.

The electron-beam response of new chemically amplified positive multi-component ARCH-resist family (ARCH and ARCH2) and the suitability of pattern transfer through single layer has been evaluated. The electron-beam lithographic parameters for thicker layers (1-2~tm) of these resists and the optimization possibilities of the exposure and etching conditions were investigated as well. Under fixed resist-handling processes, both resists exhibit high sensitivity (< 101aC/cm0 and an enormous high contrast. The study includes the effects of resist-process variations on the global 3-D resist-relief structure. Vertical side-walls of the resist profile is a necessary condition for a successful deep-, and a good CD-controlled anizotropical pattern transfer with high aspect ratio of structures into the substrate.

In this article we present results of Electron-Beam Lithographic (EBL) and Reactive ion Etching (RIE) experiments on a single layer chemically amplified novolak-based negative &Qmponent resist System (3CS). The resist type used was AZ PN114 from HOECHST AG. Direct, shaped-EBL generated single-layer resistrelief structures at O,lpm and below were RIE and RIE with magnetic enhancement transferred (i) into bulk silicon and GaAs substrates and (ii) in 400 nm Nblayer on SiO,/Si.

We report on the change of the characteristic times of the random telegraph signal (RTS) in a MOSFET operated under microwave irradiation up to 40 GHz as the microwave field power is raised. The effect is explained by considering the time dependency of the transition probabilities due to a harmonic voltage generated by the microwave field that couples with the wires connecting the MOSFET. From the dc current excited into the MOSFET by the microwave field we determine the corresponding equivalent drain voltage. The RTS experimental data are in agreement with the prediction obtained with the model, making use of the voltage data measured with the independent dc microwave induced current. We conclude that when operating a MOSFET under microwave irradiation, as in single spin resonance detection, one has to pay attention into the effects related to microwave irradiation dependent RTS changes.

Highly localized light-induced phase transformation of electron beam induced deposited carbon nanostructures (dots and squares) on noble metal surfaces is reported. The phase transformation from the amorphous phase to the disordered graphitic phase is analyzed using the characteristic Raman signatures for amorphous and graphitized carbon and conductive force microscopy. The extent of the transformation is found to be largely dependent on the plasmon absorption properties of the underlying metal fi lm. It is observed that the amorphous carbon deposits on the silver fi lms consisting of 12 nm particles with the plasmon absorption near the laser excitation wavelength (514 nm), undergo fast graphitization to a nanocrystalline or a disordered graphitic phase. This transformation results in the formation of a highly conductive carbon/metal interface with at least seven orders of magnitude lower electrical resistivity than the initial insulating interface. It is suggested that the fast graphitization of nanoscale carbon deposits might serve as an effi cient path for the formation of complex patterned nanoscale metal-carbon interconnects with high electrical conductivity.

Nanoscale 3D surface modifications, by scanning tunneling microscopy under ambient conditions, of La0.7Sr0.3MnO3 thin films have been performed. It was demonstrated that there are well defined combinations of bias voltages and scan speeds which allow for controlled surface structuring. Lateral structures with sizes down to 1.5 nm are possible to obtain. Moreover, it is possible to reproducibly control the depth of etching with half a unit cell precision, enabling design of 3D surface structures and control of the surface termination of La0.7Sr0.3MnO3 through etching.

The random telegraph signal (RTS) due to a defect at the Si/SiO 2 interface in a silicon MOSFET is strongly affected by a static magnetic field. The characteristic capture and emission times vary because of the Zeeman splitting of the defect energy levels. We observe the change of the characteristic times of the RTS by monitoring the dc current in a MOSFET operated at He3 temperature in a static magnetic field up to 12 T parallel to the current flowing from source to drain.

Electron tunneling spectroscopy is used to study drain-source current spectra of metal-oxide-semiconductor field-effect transistors ͑MOSFETs͒. Measured at liquid helium temperature ͑4.2 K͒, experimental results reveal that as drain-source voltage ͑V ds ͒ increases, the first derivative of drain-source current ͑or conductance͒ first decreases, then increases to a maximum and finally decreases again at higher V ds , which is different from the monotonous decreasing feature described by the conventional MOSFET theory. In addition, the measured MOSFET spectra show that there are fine features on the second derivative spectra, and these features may be used to extract trap information.

Fast electron pattern generator-high resolution  is a variable shaped electron beam systemderived from FEPG, specially designed for submicron writing, while keeping the multipurpose capabilities. Quarter-micron linewith is expected, thanks to a high demagnification of the stencil, reduction of the space charge effect, improvements in accurate metrology, and automatic calibration.

Electron transport at the nanometer-scale is the key to novel applications of nanomaterials in electronic and energy technologies. Due to the restricted dimensionality, one of the distinctive characteristics of nano-systems is their transport properties critically depend on structural details. Therefore, an important requirement for transport research of a specifi c nanomaterial system is to examine structures and properties in a coherent manner. In this regard, four-probe scanning tunneling microscopy (STM), which combines four independently controllable STMs with a scanning electron microscope (SEM) in the same cryogenic environment, is uniquely useful for probing electron transport on multiple length-scales and revealing how transport is coupled to the electronic and structural properties down to the atomic scale for individual nanomaterials. By utilizing this unique tool, extensive research has been undertaken to explore aspects of nanotransport, which include (a) intertwined electronic and structural phase transitions in surface supported two-dimensional structures, (b) effects of atomic defects and interwire coupling on the electronic and transport properties of ultra thin quantum wire systems, (c) grain boundary resistances in copper nanowires with one-to-one correspondence to the grain boundary structure, (d) defect scattering effects in two-dimensional electron gas systems, and (e) evaluation of transport behaviors of individual semiconductor nano-junctions and nanodevices. In this paper, transport measurement techniques are fi rst introduced with a four-probe STM and then the recent progress on its applications is reviewed with a focus on the spatially resolved electron transport at the nanometerscale. The goal is to stimulate further advancement and utilization of techniques capable of characterizing materials properties at the nanometerscale to facilitate the exploration of the great promise of nanoscience and nanotechnology.

Reactive aluminum alkoxide (ASB, aluminium sec-butoxide) was chelated using β-diketone (EAA, ethyl acetoacetate) in order to gain control over rapid hydrolysis in the course of the sol-gel process. Derived chelates were analysed using several NMR spectroscopic techniques: one-dimensional 1H, 13C, 27Al NMR and two-dimensional COSY, HSQC and DOSY. The NMR analysis enabled identification of the formed chelate species, as well as determination of their quantitative relationships. Several complexation products were observed: tris-chelated monomer, Al(EAA)3, bis-chelated dimmer, Al2(OnBu)4(EAA) 2, tris-chelated dimmer, Al2(OnBu)3(EAA)3, tetra-chelated dimmer, Al2(OnBu)2(EAA)4, and monochelated trimer, Al3(OnBu)8(EAA). Of the formed oligomer compounds, this is the first evidence of Al2(OR)3L3 in any alkoxide and β-ketoester or β-diketone combination. Aluminium sec-butoxide and ethyl acetoacetate complexes Al2(OnBu)4(EAA) 2 and Al2(OnBu)2(EAA)4 were also observed for the first time. With th...

This paper presents a method to obtain submicron-and nanometer structures of different oxide films and heterostructures combining e-beam lithography and chemical etching. The most relevant advantage of this method is that structures of tens of microns in length and below ∼100 nm width can be produced, keeping the intrinsic bulk film properties, as proven by electrical transport measurements. In this way our method provides a bridge that connects the attractive properties of oxide films and the nanoworld.

This paper describes the equipment and software necessary to integrate a variable temperature setup and an automated data collection system to extract semiconductor device modeling parameters over a wide temperature range. The cryogenic test station with a temperature range of 1.8-300 K is used for semiconductor device evaluation with the test structure mounted in an 8 pin, TO-99 style header. The system consists of a custom low temperature apparatus and stateof-the-art electrical instrumentation under control of a minicomputer. A unique circuit which biases the device under test at low temperatures is described which avoids heating of the sample. The system has been implemented with commercially available software that allows a computer host to collect and store device data from instrumentation on the interface bus. An electromagnet suitable for Hall studies with a custom designed 1.1-kW programmable power supply for automated control of the magnetic field completes the system. The cryogenic test station has been used to study the characteristics of n-channel Hall effect MOSFET's from 1.8 K to room temperature, and a method to extract the MOS modeling parameters of threshold voltage and effective mobility is described.

Institute of Electron Technology (u) and Institute of Physics (b) , Technical tinicersity, WrocEazi,l) Modified PRIMA-Polymers for Masks in Ion Beam Lithography2) M. Kism (a) arid E. OLESZKIFWICZ (b) l o n scnsitive polymers are modified for submicron structure technology application. Di-butyl maleate is usrd as an impurity in P?rPMIA to modify the plasticity and continuity of the resist films. Experiments performed using light ions with energies of 30 to 50 keV show the improved contrast, sensitivity, and geometric< stability of the new material. With the modification ratio increase up to 20% the sensitivity inrreases by about 250/; and the contrast inrreases t o 30 to 50y,, (dependent on the ion energy). II'hen the ion range exceeds the resist thickness, secondary effecth arc visible. On a modifii: drs polymPres ionosensibles nu point de vne dutilisation en technologie des semiconducteurs. Lr nialkate bi-butylique utilis6 comme impuret6 L PMMB amkliore la plasticit6 et la continnit6 dcs couches de polymbres. Les espbriences d h o n t r e n t I'amClioration du contrast t t de la, stabiliti: ghmetrique des conches minces irradiks par les ions l6gers d'knergies de 30 8. 50 keV. Si le coefficient dc modifiration angnirnte jusqu'L 20'36, la sensibilit6 augmente dc 2504, le contraste de 30 L 500,, (en fonction d'i:nerpie des ions). Si la distance d i m s est plus grande que 1'6paisscnr de la coache mincr, les effets sccondaires appnraissent.

A nanometer electron beam lithography system has been developed and used for fabricating sub-0.1µm gate MOSFETs. The system uses a Zr/O/W thermal field emitter (TFE) and has a 5-nm-diameter beam at a current of 100 pA, and an acceleration voltage of 50 kV. A 10-nm line in PMMA resist on a thick Si substrate was demonstrated. We develop an inorganic resist, LiXA11_XF, which shows a potential for high resolution lithography less than 10 nm. A chemically amplified negative resist was used as a single layer mask for MOS FET gate fabrication, and showed high resolution less than 0.1 µm width. Proximity effect correction was applied to the gate lithography, resulting in excellent line width control even less than 0.1µm. Operation of a 40-nm-poly-silicon gate NMOSFET was confirmed.

The electron-beam response of new chemically amplified positive multi-component ARCH-resist family (ARCH and ARCH2) and the suitability of pattern transfer through single layer has been evaluated. The electron-beam lithographic parameters for thicker layers (1-2~tm) of these resists and the optimization possibilities of the exposure and etching conditions were investigated as well. Under fixed resist-handling processes, both resists exhibit high sensitivity (< 101aC/cm0 and an enormous high contrast. The study includes the effects of resist-process variations on the global 3-D resist-relief structure. Vertical side-walls of the resist profile is a necessary condition for a successful deep-, and a good CD-controlled anizotropical pattern transfer with high aspect ratio of structures into the substrate.

Regular arrays of sub-0.5 pm tips are of increasing interest, for example, as field emitters, calibration structures, or, in our particular case, as collector surfaces for sub-l~n dust particles in a space experiment. This contribution describes the preparation of 1 x 1 cm 2 arrays of microcolumns with a high aspect ratio (10:1) and a diameter in the sub-micrometer range (150-300 nm). The process is based upon a chemically amplified novolak resist (CAR), electron beam lithography, and ECR plasma etching.

We report on e-beam lithographic (EBL) and reactive ion etching (RIE) experiments with the positive chemically amplified resist (CAR) CAMP6 used for the fabrication of silicon structures ranging in size from the nanometer scale up to the micron scale in relatively thick resist film. Direct-write EBL at 30 keV was used to study the pre-and post-exposure processing on the resulting resist-relief structures. We measured the basic resist characteristics and also the influence of proximity effects. The resolved single-layer resist-relief structures at optimised process conditions have shown high aspect ratios with nearly vertical side-walls and T-top profiles in 0.6-1.7 Ixm thick films up to nanometer lateral dimensions. The paper will discuss the deep pattern transfer results into the underlying 2.6 Ixm thick SiO 2 and/or directly into the Si-substrate by using RIE. We achieved excellent vertical side-walls free of passivation. The building of facets was observed to be on an acceptable scale.

R l • • I • • • esolution limits for electron-beam ithography by A. N. Broers ''Copyright 1988 by International Business Machines Corporation. Copying in printed form for private use is permitted without payment of royalty provided that (1) each reproduction is done without alteration and (2) the Journal reference and IBM copyright notice are included on the first pa^. The title and abstract, but no other portions, of this paper may be copied or distributed royalty free without further permission by computer-based and other information-service systems. Permission to republish any other portion of this paper must be obtained from the Editor. electron bombardment. In ttiese cases no intermediate fabrication process would be used, and It might be possible to reach dimensions comparable to the beam diameter.

We have succeeded in obtaining epitaxial yttrium-iron garnet (YIG) micropatterns on a gadolinium-gallium garnet (GGG) substrate by a metalorganic decomposition method with electron-beam (EB) irradiation. We have demonstrated that metal-octylates of Y and Fe showed negative exposure behavior for EB irradiation. X-ray diffraction measurements indicated that the YIG micropatterns were epitaxially well grown on a GGG(111) substrate. The magnetization curve of the YIG micropatterns showed a clear hysteresis loop and the saturation magnetization was estimated to be approximately 100 emu/cm 3 , which is consistent with that of bulk YIG.

In situ transmission electron microscope (TEM) characterization techniques provide valuable information on structure–property correlations to understand the behavior of materials at the nanoscale. However, understanding nanoscale structures and their interaction with the electron beam is pivotal for the reliable interpretation of in situ/ex situ TEM studies. Here, we report that oxides commonly used in nanoelectronic applications, such as transistor gate oxides or memristive devices, are prone to electron beam induced damage that causes small structural changes even under very low dose conditions, eventually changing their electrical properties as examined via in situ measurements. In this work, silicon, titanium, and niobium oxide thin films are used for in situ TEM electrical characterization studies. The electron beam induced reduction of the oxides turns these insulators into conductors. The conductivity change is reversible by exposure to air, supporting the idea of electron be...

P. Amo-Ochoa, a D. Olea, b A. Guijarro, c SS Alexandre, b F. de Jesús, a JM Soler, b P. ... J. de Pablo, b J. Gómez-Herrero, b F. Zamora. c ... Madrid, Departamento de Química Inorgánica (C-VIII), 28049 Madrid, Spain. felix.zamora@uam.es ... In the search of molecular wires ...

Coherent coupling between a large number of qubits is the goal for scalable approaches to solid state quantum information processing. Prototype systems can be characterized by spectroscopic techniques. Here, we use pulsed-continuous wave microwave spectroscopy to study the behavior of electrons trapped at defects within the gate dielectric of a sol-gel-based high-k silicon MOSFET. Disorder leads to a wide distribution in trap properties, allowing more than 1000 traps to be individually addressed in a single ...

We report experimental results on the kinetics of the electron-beam-induced reduction of WO, by in situ high-resolution electron microscopy. Electron-beam irradiation of WO, results in complete reduction to W. The process is surfaceinitiated through desorption of oxygen from the crystal surface, and the subsequent growth of tungsten was found to be a diffusion-controlled process. The damage rate follows a para-linear curve, that is, an initially parabolic damage rate degenerating into a linear rate. The epitaxial relationship between WO, and W was found to be (OOl)wo3//(l10)w The WO, lattice has a critical nucleus size of about 2.6nm.

The electron beam exposure characteristics of sputtered AlO x and spin-coatable Al 2 O 3 resists are compared and contrasted. When exposed to an electron beam, sputtered AlO x resists on a silicon substrate undergo an intense mass loss. However, electron energy loss spectroscopy shows that even after a prolonged exposure some aluminum and oxygen remains on the silicon surface. Spin-coatable Al 2 O 3 resist was prepared by reacting aluminum tri-sec-butoxide, Al͑OBu s) 3 , with acetylacetone ͑AcAc͒ in isopropyl alcohol. These are negative tone resists and they are Ͼ10 6 times more sensitive to an electron beam than the sputtered AlO x , bringing its sensitivity very close to high resolution organic resists such as calixarene. The exposure properties of spin-coatable and sputtered aluminum oxide resists are discussed together with their sensitivity, damage mechanisms, line edge roughness, and etching characteristics. A brief note on the change of methodology of resist design is added when inorganic resists are to be used in high resolution electron beam nanolithography.

A proximity effect occurs when two features having a close proximity are exposed using conventional organic electron-beam resists, subsequently causing overexposure of the region between the two features and ultimate broadening of the features. In this study, we employ probes of a through-focal series to irradiate amorphous AlF 3 (a-AlF 3 ) inorganic films. A proximity effect of a very different nature is also observed while employing the a-AlF 3 films as self-developing electron-beam resists. Such an effect distorts the closely spaced features and sets a limit on the proximity of those nanometer-scaled features. According to the results of electron microscopy obtained while examining the peculiar behavior of the proximity effect, mass-transport phenomena are critical in the damaging behavior of the a-AlF 3 films. Besides, our results presented herein demonstrated the ability of the through-focal probes to produce aluminum nanostructures of varying sizes in thin films containing a-AlF 3 self-developing resists.

This paper presents a number of new results on direct nanometre-scale electron beam drilling and writing of inorganic materials. It is demonstrated that drilling thresholds for a number of materials can be exceeded using a conventional thermionic tungsten filament in a standard electron microscope. Results are presented not only for materials (such as sodium beta-alumina) in which drilling is a well established phenomenon, but also for a number of materials in which drilling has not previously been reported (including K3CuF6, MOO3, and an amorphous Y-Ba-Cu-O phase close to the superconducting composition). Preliminary results on the temperature dependence of electron drilling are given, and it is shown that it is easier to drill amorphous alumina at liquid nitrogen temperature than at room temperature. It is demonstrated that using condensed gases upon a substrate, reactive electron beam etching of the substrate on a nanometre scale may be performed; this chemically-assisted drilling process allows us to write in a number of materials (such as C films) which are not normally beam sensitive. Although an electron beam of circular cross-section normally drills circular holes, it is shown that square holes may be drilled in MgO crystals using a circular cross-section beam.

Electron beam-induced crystallization studies in amorphous FeF 3 films using electron energy loss spectroscopy ͑EELS͒ are discussed in this letter. Time-resolved EELS studies show that the coordination polyhedra in amorphous FeF 3 (a-FeF 3) are randomly arranged FeF 6 octahedra. They arrange themselves to give long range order during crystallization to FeF 2 and FeF 3 under the electron beam. Changes in the d-band occupancy by one electron as well as the sensitivity of the ratio of the Fe L 3 and L 2 edges to the electronic configuration of the iron ion are clearly seen during the crystallization process.

Transmission electron microscopy is used to investigate electron-induced crystallization of thermally evaporated amorphous AlF 3 ͑a-AlF 3). It is shown that this material undergoes a very complicated crystallization process with three crystalline substances ͑Al, AlF 3 , and Al 2 O 3) formed as the dose increases. The sequence of the crystallization is highly sensitive to the presence of water, which inhibits radiolytic dissociation of a-AlF 3 into Al and fluorine, reduces the dose required for the crystallization of a-AlF 3 , and causes the transformation of AlF 3 into Al 2 O 3 .

The electrical and emission properties of as deposited and annealed SiO x ͑Si͒ films have been investigated. The films with thicknesses of 10-100 nm were obtained by thermal evaporation of silicon powder in vacuum ͑2.7-4.0͒ ϫ 10 −3 Pa on flat Si substrates and Si tip arrays. The atomic force microscopy investigations of the surface morphology indicated the presence of nanoprotrusions on surface of the initial SiO x ͑Si͒ films with height up to 20 nm and curvature radius of the nanoprotrusions about 3-5 nm. As a result of the thermal annealing, the film surface becomes more uniform and its morphology is characterized by nanoprotrusions with height in the range of 1-3 nm. At low electric fields the I-V characteristics of dark current through the initial SiO x ͑Si͒ films correspond to Poole-Frenkel transport mechanism. The Fowler-Nordheim tunneling dominates at higher electric fields. As to annealed SiO 2 ͑Si͒ films, the modified Fowler-Nordheim electron tunneling through trapezoidal SiO 2 barrier between silicon nanoclusters restricts the current flow. The effective electron field emission from Si tip arrays coated with nanocomposite SiO x ͑Si͒ and SiO 2 ͑Si͒ films was observed. The results of the electron field emission from surface of SiO x ͑Si͒ films into vacuum show an emission current density of 0.25ϫ 10 −5 A/cm 2 at macroscopic electric fields of ͑5-6͒ ϫ 10 5 V / cm. The field emission from thermally annealed samples was not observed in the whole range of the applied voltages. In the contrary, for the case of thermally annealed samples subjected to the following partial etching in HF : H 2 O solution, the emission increases in comparison with initial samples. In this case the field emission appears already at an electric field of 1.5ϫ 10 5 V / cm and the maximum current density increases up to the value of ϳ3 ϫ 10 −5 A/cm 2. The current peaks are revealed on emission I͑V͒ characteristics built in J͑E͒ coordinates. The models for explanation of peculiarities of the electrical conductivity and electron field emission from nanocomposite films are discussed.

We report on e-beam lithographic (EBL) and reactive ion etching (RIE) experiments with the positive chemically amplified resist (CAR) CAMP6 used for the fabrication of silicon structures ranging in size from the nanometer scale up to the micron scale in relatively thick resist film. Direct-write EBL at 30 keV was used to study the pre-and post-exposure processing on the resulting resist-relief structures. We measured the basic resist characteristics and also the influence of proximity effects. The resolved single-layer resist-relief structures at optimised process conditions have shown high aspect ratios with nearly vertical side-walls and T-top profiles in 0.6-1.7 Ixm thick films up to nanometer lateral dimensions. The paper will discuss the deep pattern transfer results into the underlying 2.6 Ixm thick SiO 2 and/or directly into the Si-substrate by using RIE. We achieved excellent vertical side-walls free of passivation. The building of facets was observed to be on an acceptable scale.

A silicon on insulator field effect transistor for cryogenic operation has been fabricated using a sol-gel derived TiO 2 electron beam resist as a high-k gate dielectric and characterized over a range of temperatures. The TiO 2 dielectric layer allows too large a gate leakage current for good device operation at room temperature, but the leakage current is strongly suppressed at cryogenic temperatures and good transistor characteristics were observed. The temperature dependence of the gate leakage current suggests that Frenkel-Poole and trap-assisted tunneling dominates the conduction in the dielectric layer. The drain current shows peaks at certain frequencies under continuous wave microwave irradiation, which may be caused by the resonance of electrons trapped in defects at the TiO 2 / SiO 2 interface. These resonances offer the possibility to manipulate single electrons for nonclassical information processing.

Manipulation of carrier densities at the single electron level is inevitable in modern silicon based transistors to ensure reliable circuit operation with sufficiently low threshold-voltage variations. However, previous methods required statistical analysis to identify devices which exhibit random telegraph signals (RTSs), caused by trapping and de-trapping of a single electron. Here, we show that we can deliberately introduce an RTS in a silicon nanowire transistor, with its probability distribution perfectly controlled by a triple gate. A quantum dot (QD) was electrically defined in a silicon nanowire transistor with a triple gate, and an RTS was observed when two barrier gates were negatively biased to form potential barriers, while the entire nanowire channel was weakly inverted by the top gate. We could successfully derive the energy levels in the QD from the quantum mechanical probability distributions and the average lifetimes of RTSs. This study reveals that we can manipulate individual electrons electrically, even at room temperature, and paves the way to use a charged state for quantum technologies in the future.

Electron beam deposition of tungsten from W(CO)6 has been studied for a range of different height deposits. The resistance of the deposited tracks was found to decrease with increasing height implying that thicker deposits have a higher metallic cross section. It was also found that when the current limits were increased to values in excess of 100 µA, the resistance decreased with successive voltage cycles and increasing current limit. This improvement continued until a point where the structure of the deposit appeared to start breaking down and its resistance increased slightly. Subsequently, the structure was found to break near to the contact. It was also found that as the resistance of the deposit decreased, the structure of the deposited tracks changed implying that ohmic heating induced high enough temperatures within the deposit to be able to cause the structure of the material to change.

The random telegraph signal (RTS) due to a defect at the Si/SiO 2 interface in a silicon MOSFET is strongly affected by a static magnetic field. The characteristic capture and emission times vary because of the Zeeman splitting of the defect energy levels. We observe the change of the characteristic times of the RTS by monitoring the dc current in a MOSFET operated at He3 temperature in a static magnetic field up to 12 T parallel to the current flowing from source to drain.

The random telegraph signal (RTS) due to a defect at the Si/SiO 2 interface in a silicon MOSFET is strongly affected by a static magnetic field. The characteristic capture and emission times vary because of the Zeeman splitting of the defect energy levels. We observe the change of the characteristic times of the RTS by monitoring the dc current in a MOSFET operated at He3 temperature in a static magnetic field up to 12 T parallel to the current flowing from source to drain.

In this work, we demonstrate that conductive atomic force microscopy ͑C-AFM͒ is a very powerful tool to investigate, at the nanoscale, metal-oxide-semiconductor structures with silicon nanocrystals ͑Si-nc͒ embedded in the gate oxide as memory devices. The high lateral resolution of this technique allows us to study extremely small areas ͑ϳ300 nm 2 ͒ and, therefore, the electrical properties of a reduced number of Si-nc. C-AFM experiments have demonstrated that Si-nc enhance the gate oxide electrical conduction due to trap-assisted tunneling. On the other hand, Si-nc can act as trapping centers. The amount of charge stored in Si-nc has been estimated through the change induced in the barrier height measured from the I-V characteristics. The results show that only ϳ20% of the Si-nc are charged, demonstrating that the electrical behavior at the nanoscale is consistent with the macroscopic characterization.

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.