Papers by Ramachandran Muralidhar
IEEE Journal of the Electron Devices Society, 2018
In this paper, we propose the extendibility of ultra-thin body and box (UTBB) devices to 7 and 5 ... more In this paper, we propose the extendibility of ultra-thin body and box (UTBB) devices to 7 and 5 nm technology nodes focusing on electrostatics. A difficulty in scaling traditional UTBB is the need for SOI scaling to about one fourth of the gate length. We propose a U-channel fully depleted silicon on insulator architecture that starts off with a thicker SOI (8-11 nm) and has a U-shaped channel enabled by a recessed metal gate. This device improves the electrostatics by increasing the overall gate length at fixed metal gate opening, mitigating drain field coupling to the source due to the recessed metal gate region and having thin SOI below the center of the device (4-5 nm). Modeling shows that good electrostatics can be maintained at small metal gate opening to enable pitch scaling. This device provides lower cost options for mobile and IOT technologies.
Sensors, 2019
We present field deployment results of a portable optical absorption spectrometer for localizatio... more We present field deployment results of a portable optical absorption spectrometer for localization and quantification of fugitive methane (CH4) emissions. Our near-infrared sensor targets the 2ν3 R(4) CH4 transition at 6057.1 cm−1 (1651 nm) via line-scanned tunable diode-laser absorption spectroscopy (TDLAS), with Allan deviation analysis yielding a normalized 2.0 ppmv∙Hz−1/2 sensitivity (4.5 × 10−6 Hz−1/2 noise-equivalent absorption) over 5 cm open-path length. Controlled CH4 leak experiments are performed at the METEC CSU engineering facility, where concurrent deployment of our TDLAS and a customized volatile organic compound (VOC) sensor demonstrates good linear correlation (R2 = 0.74) over high-flow (>60 SCFH) CH4 releases spanning 4.4 h. In conjunction with simultaneous wind velocity measurements, the leak angle-of-arrival (AOA) is ascertained via correlation of CH4 concentration and wind angle, demonstrating the efficacy of single-sensor line-of-sight (LOS) determination of...
Electrochimica Acta, 2016
Solid-state programmable metallization cells have attracted considerable attention as memristive ... more Solid-state programmable metallization cells have attracted considerable attention as memristive elements for Redox-based Resistive Random Access Memory (ReRAM) for low-power and low-voltage applications. In principle, liquid-state metallization cells could offer the same advantages for aqueous systems, such as biomedical lab-on-a-chip devices, but robust resistive switching has not yet been achieved in liquid electrolytes, where electrodeposition is notoriously unstable to the formation of fractal dendrites. Here, the recently discovered physics of shock electrodeposition are harnessed to stabilize aqueous copper growth in polycarbonate nanopores, whose surfaces are modified with charged polymers. Stable bipolar resistive switching is demonstrated for 500 cycles with <10s retention times, prior to any optimization of the geometry or materials. In recent years, memristive elements 1 based on internal redox-reactions have attracted intense interest for applications such as non-volatile Random Access Memory. 2-4 Resistive switching in solid-state ultra-thin films is widely viewed as a potential replacement for flash memory in devices requiring lower power, lower voltage, and higher programming speed. A popular class of these Redox-based Resistive Random Access Memories (ReRAM)
Process of forming an electronic device including a layer of discontinuous storage elements
Methods for programming a floating body nonvolatile memory
Semiconductor Device with High K Dielectric Control Terminal Spacer Structure
Programming, erasing, and reading structure for an NVM cell
MRS Proceedings, 2004
ABSTRACTSilicon nanocrystals can be used in non-volatile memory devices to reduce susceptibility ... more ABSTRACTSilicon nanocrystals can be used in non-volatile memory devices to reduce susceptibility to charge loss via tunnel oxide defects, allowing scaling to smaller sizes than possible with conventional Flash memory technology. In order to optimize device performance, it is desirable to maximize the nanocrystal density and surface coverage, while maintaining sufficient inter-crystallite separation to limit electron tunneling between adjacent crystallites. Ideally, crystallite densities in excess of 1012cm-2 with relatively narrow particle size distributions must be obtained, posing a significant challenge for process development and control. In order to facilitate development of such a process, a rate-expression-based model has been developed for the nucleation and growth of silicon nanocrystals on SiO2 in a CVD process. The model addresses the phenomena of nucleation, growth, and coalescence and includes the effects of exclusion zones surrounding the growing nuclei. The model uses...
Silicon Nanocrystal Charging by Hot electron Tunneling
ABSTRACT
Gate Disturb Reduction in a Silicon Nanocrystal Flash EEPROM by Means of Natural Threshold Voltage Reduction
ABSTRACT First Page of the Article
IEEE Journal of the Electron Devices Society, 2014
The SOI symmetric lateral bipolar transistor is uniquely suitable for operation at high injection... more The SOI symmetric lateral bipolar transistor is uniquely suitable for operation at high injection currents where the injected minority carrier density in the base region is larger than the base doping concentration. Transistors operating in high-injection can achieve record-high drive currents on the order of 3-5 mA/µm. The commonly used Shockley diode and bipolar current equations are modified to be applicable for all injection levels. Excellent agreement is shown between measured and modeled currents for data at V BC = 0. A novel partially depleted-base design can further increase the drive current and the current gain, especially at low V BE .
Interconnect wiring switches and integrated circuits including the same
Bulk finFET with super steep retrograde well
Pattern and Process Dependencies in Copper Damascene Chemical Mechanical Polishing Processes
In this paper we present experimental data that shows the dependence of copper dishing and oxide ... more In this paper we present experimental data that shows the dependence of copper dishing and oxide ero- sion on pitch and pattern density, as well as on polishing process parameters including table speed, do wn force, and process sequence. Specifi cally, the data shows that the degree of dishing and erosion strongly depends on both the processing parameters and layout factors (density and pitch). We find that a multiple step polish is able to achie ve better polishing results compared to a single step polish process. Furthermore, we observe an interesting break point for both erosion and dishing at an oxide line space of approximately 100 μ m. It is also observed that the interaction distance, the length o ver which a pattern parameter is com- puted, is significantly shorter than that of conventional oxide polish.
Transport in Porous Media, 1993
A major aspect of describing transport in heterogeneous media has been that of relating effective... more A major aspect of describing transport in heterogeneous media has been that of relating effective diffusivities to the topological properties of the medium. While such effective transport coefficients may be useful for mass fractals or under steady state conditions, they are not adequate under transient conditions for self-similar pore fractal media. In porous formations without scale, diffusion is anomalous with the mean-squared displacement of a particle proportional to time raised to a fractional exponent less than unity. The objective of this review is to investigate the nature of the laws of diffusion in fractal media using the framework of linear response theory of nonequilibrium statistical mechanics. A Langevin/Fokker-Planck approach reveals that the particle diffusivity depends on its age defined as the time spent by the particle since its entry into the medium. An analysis via generalized hydrodynamics describes fractal diffusion with a frequency and wave number dependent diffusivity.
Physical Review A, 1992
The size-specific coagulation frequencies of fractal aggregates formed by the simulation of di8'u... more The size-specific coagulation frequencies of fractal aggregates formed by the simulation of di8'usionlimited cluster-cluster aggregation in two and three dimensions are determined from dynamic-scaling spectra by an inverse-problem approach. The four cases considered are twoand three-dimensional aggregation in which the cluster difFusivity is independent and dependent upon the mass of the cluster. The frequencies derived from this approach describe the transient simulation results very well, the predictions being better than those with the Smoluchowski Brownian-coagulation frequency [Phys. Z. 17, 557 (1916)]modified by scaling arguments in three dimensions. Furthermore, frequencies are obtained for two-dimensional aggregation for which physical models have been evasive. The validity of the mean-field equation with a time-independent homogeneous frequency is examined. It is found that the mean-Geld approximation is valid in the range of simulation results but progressively deteriorates with time. The power of the inverse-problem approach here lies in its yielding size-specific aggregation rates of particles whether or not physical models are available.
Diffusion on two-dimensional percolation clusters: Influence of cluster anisotropy
Physical Review A, 1991
Study of Single Silicon Quantum Dots’ Band Gap and Single-Electron Charging Energies by Room Temperature Scanning Tunneling Microscopy
Nano Letters, 2008
Scanning tunneling spectroscopy in the shell-filling regime was carried out at room temperature t... more Scanning tunneling spectroscopy in the shell-filling regime was carried out at room temperature to investigate the size dependence of the band gap and single-electron charging energy of single Si quantum dots (QDs). The results are compared with model calculation. A 12-fold multiple staircase structure was observed for a QD of about 4.3 nm diameter, reflecting the degeneracy of the first energy level, as expected from theoretical calculations. The systematic broadening of the tunneling spectroscopy peaks with decreasing dot diameter is attributed to the reduced barrier height for smaller dot sizes and to the splitting of the first energy level.
Journal of Statistical Physics, 1990
The coagulation frequency is the key ingredient in the population balance (Smoluchowski) equation... more The coagulation frequency is the key ingredient in the population balance (Smoluchowski) equation of coagulation kinetics. An inverse problem is formulated to extract the coagulation frequency from transient size distributions when these distributions are self-similar. Two numerical examples illustrate the procedure. The first demonstrates the inverse problem for the recovery of singular coagulation frequencies, while the second shows the procedure when self-similarity is approximate. Transient droplet coagulation experiments in a turbulent flow field have been performed. The resulting size distributions are observed to be self-similar. The inverse problem is used to determine the drop coagulation frequency. This frequency shows significant deviation from the coagulation frequencies derived from simple models of drop~lrop interactions in a turbulent flow field.
Journal of Colloid and Interface Science, 1989
An inverse problem is formulated to estimate bivariate kinetic coefficients for irreversible aggr... more An inverse problem is formulated to estimate bivariate kinetic coefficients for irreversible aggregation processes from measurements of transient size spectra. The approach is applicable in situations where the transient spectra exhibit similarity behavior, No assumptions regarding the physical nature of the agglomeration process or any properties of the coagulation kernel are made. The formulation is a generalization of our earlier one for homogeneous agglomeration frequencies. In view of the fact that the inverse problem is ill-posed, regularization techniques are employed to facilitate inversion. Numerical examples for homogeneous as well as n0nhomogeneous agglomeration kernels are presented to illustrate the methodology. The results indicate .that accurate data can yield good estimates of the frequency. It is thus shown that self-preserving spectra can be used effectively to estimate the binary clustering coefficients in situations where they are unknown.
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Papers by Ramachandran Muralidhar