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In this work, we study van der Waals (vdW) heterostructures consisting of the emerging photonic material, 2-dimensional (2D) InSe, with the lattice-matched 2D materials silicene, germanene and antimonene, using ab-initio simulations. We employ density functional theory (DFT) to calculate the structural and electronic properties of the vdW hetero-bilayers. The optical spectra of the systems are evaluated by solving the Bethe-Salpeter equation (BSE) on top of the GW quasiparticle bands. A strong response in the IR-visible region of the optical spectra is seen in case of InSe-Si and InSe-Ge vdW lattice whereas the InSe-Sb structure shows better performance in the visible-UV region, with better prospect of excitonic charge separation. A good absorbance in the IR-visible and the visible-UV region, can be achieved with these structures with computed theoretical photocurrent densities significantly larger than conventional photovoltaic materials. While individually the vdW structures can be useful in photonic applications, the complimentary nature of absorption with InSe-Sb and InSe-Si/Ge structures can also be utilized in multi-junction heterostructure solar cells.

Here, we report a study of carrier transport and thermoelectric properties of silicene/germanene nanoribbon (SiNR/GeNR) interconnects of varying shapes (namely, “V,” “L,” “U,” and “S” shaped) with empirical tight binding—nonequilibrium Green’s function approach. Our simulation shows that a significant reduction in both electron and phonon transmission in such differently shaped NRs compared to perfect ones. In terms of thermoelectric properties, Seebeck coefficient ( $\mathbb {S}$ ) variation in the range of −72.3 to $3.52~\mu \text{V}$ /K at 300 K for SiNR and −176 to $-\textsf {95.5}\,\,\mu \text{V}$ /K at 300 K for GeNR is observed in different pattern conditions. For Peltier coefficient ( $\pi $ ), these ranges are −0.23 to 0.001 V for SiNR and −0.053 to −0.011 V for GeNR at 300 K. Simulation also shows significant change in thermoelectric figure of merit ( $\textit {ZT}$ ) for a different pattern and temperature with peak $\textit {ZT}~0.09$ at 800 K for “U”-shaped SiNR and 0.80 at 400 K for “L”-shaped GeNR.

In this work with density functional theory calculations, we investigated the van der Waals heterostructure (vdWh) between metallic 2 dimensional (2D) sheets of Cu and Ag with monolayer 1T’ ReS 2 . With structural relaxations inclusive of van der Waals forces, the stable interfacial configuration were optimized. Thereafter the various properties of the vdWh, such as density of states, electron density, total potential and electron localization function, were thoroughly investigated. The computational studies show that both the heterostructures display a metallic to semi-metallic nature, with the Cu-ReS 2 structure being more metallic. In terms of electrostatics, a larger concentration of electrons were observed on Cu as compared to Ag for the two interfaces, while an electron gas like feature could be seen between the 2D Ag and ReS 2 layers. The results are of interest for 2D nanoelectronics devices and flexible electronics applications.

Ni or Ga doping is well studied in literature. However, a Ga/Ni co-doped ZnO brings in complex competing mechanisms of electron mobility and electron localization. A sol-gel prepared solid solution of Ga/Ni co-doped ZnO with hexagonal wurtzite structure (P63mc space group) is studied in detail to correlate the electronic properties to the structure of the materials. Lattice strain studies correlated to these changes in the electronic properties. The drastic reduction in native defects was detailed using the photoluminescence study of Ni/Ga co-doped ZnO. Lattice and phonon studies were used to explain the lattice strain in the ZnO lattice. The % Sensitivity of UV (290 nm), blue (450 nm), green (540 nm) and red (640 nm) wavelengths were tested and correlated with the defects. Additionally, the photo-catalytic dye degradation of toxic methylene blue was investigated and explained with changes in carrier concentration and mobility. The reason behind the conductive parameters was examined theoretically and a possible reason was found in terms of changes in electron localization due to increasing Ni/Ga concentration.

In this work the lithiation and sodiation properties of 2-dimensional (2D) AlN sheets are studied from density functional theory (DFT) simulations. 2D AlN showed theoretical specific capacity of 500.8 and 385.3 mA h g−1, maximum open circuit voltage of 1.49 and 1.86 V and diffusion barriers 0.40 and 0.15 eV, for Li and Na adsorption respectively. The calculations show 2D AlN as a possible alternative as anode material in Li-ion and Na-ion batteries. Further the high specific capacity and small diffusion barriers for Na atoms can make 2D AlN useful in supercapacitors. The change in carrier transport properties due to Li/Na adsorption on monolayer AlN can also be useful in chemical/bio-sensors and nanoelectronics devices.

We report the atomistic study of a carbon nanotube (CNT) mass transport memory with Fe, Co and Ni nanoparticle shuttles encapsulated within it. For our calculation the extended-Huckel theory has been employed to study the various electronic, electrostatic and transport of such devices. The simulation results show that all the three sets of CNT devices with Fe, Co and Ni nano-shuttle are efficient in performance in terms of distinguishable electronic properties, with regard to nanoparticle position and type of nanoparticles. There is observable change in transmission w.r.t. change of positions and type of nanoparticles. Fe@CNT shows more metallic nature of transmission as compared to Co@CNT and Ni@CNT. All the devices show minimal loss of coherence in transmission in terms of conducting eigenstates and elastic backscattering. The Ni and Co nanoparticle captured more amount of charge as compared to Fe nanoparticle, and can offer superior performance in case of charge sensing detection of memory states.

The paper presents an ab initio study of the 2-D insulators and their effect on the performance of a magnetic tunnel junction memory (MTJ) device. MTJ devices has been considered as an alternate to the charge based data storage cells due to its spin-polarised operation and high scaling probability. The use of 2-D insulators like X-(OH)2 (X: Ca and Mg) and h-BN (hexagonal-Boron Nitride) in such device would be interesting. The authors have calculated the band structures, density of states and effective mass of electrons and holes for the mono-layer of these three non-conventional 2-D insulators using the first principle calculations in density functional theory framework using Quantumwise ATK tool. The ab initio calculation yielded band gap (Eg) of 4.633, 4.685 and 4.249 eV for h-BN, Ca(OH)2 and Mg(OH)2, respectively. The effective mass of electrons was calculated as 0.621, 0.604 and 0.478 for single layer h-BN, Ca(OH)2 and Mg(OH)2, respectively. While for holes it is 0.834, 0.446 and 0.407, respectively for h-BN, Ca(OH)2 and Mg(OH)2. The MTJ device properties as tunneling-magneto resistance, differential TMR, parallel and anti-parallel resistance, differential resistance and spin transfer torque components (in-plane and out-of-plane) with these materials as composite dielectric has been reported in this paper using MTJ Lab tool. The performance of MTJ memory device with h-BN based composite dielectric is found better.

The recently discovered 2 dimensional form of antimony can be of sufficient interest in lithium/sodium ion batteries (LIB/NIB) owing to its successful experimental isolation into free standing flakes, good electrical properties and excellent stability. In this work we report ab-initio studies on the Lithium (Li) and Sodium (Na) atom adsorption properties of free standing monolayer antimonene (Sb) sheet. With generalized gradient approximation (GGA) with Perdew–Burke–Ernzerhof (PBE) exchange correlation, inclusive of van der Waals correction by Grimme's DFT-D2 method, we evaluate the lithiation/sodiation mechanisms of the buckled honeycomb structure of monolayer Sb. Our calculations show 2D Sb as a promising candidate for anode material in NIB with specific capacity of 320 mAh g−1, open circuit voltage of upto 1.22 V and small diffusion barrier of 0.114 eV. The high capacity and good Na diffusion properties also hold promise for Na-air batteries and supercapacitors.

We investigate the effects of uniaxial tensile and compressive strain on the material and transport properties of semiconducting Carbon Nanotube and the device properties of Blue-Phosphorene-CNT heterojunction devices. We see that the material and transport properties of the semiconducting CNT can be tuned through the application of uniaxial strain. The device properties of the heterojunction can also be modulated by strain. The variation in the current is significant in tensile strain zone.

In this work, we present a computational study on the possibility of strain engineering in monolayer Black Phosphorus (black P) and Blue Phosphorus (blue P) based MOSFETs. The material properties like band structure, carrier effective masses, carrier densities at band extrema are evaluated using Generalized Gradient Approximation (GGA) in Density Functional Theory (DFT).Thereafter self-consistent Non-Equilibrium Greens Function (NEGF) simulations are carried out to study the device performance metrics (such as output characteristics, ON currents, transconductance etc.) of such strained black P and blue P based MOSFETs. Our simulations show that carrier effective masses in blue P are more sensitive to strain applied in both zigzag and armchair directions. Blue P is more responsive in strain engineering for n-MOS and p-MOS. Except for black P based FETs with strain in armchair direction, overall the blue P (black P) n-MOSFET (p-MOSFET) show moderate to significant improvement in performance with tensile (compressive) strain in the transport directions., 16 pages

In this work by means of ab-initio calculations and Non equilibrium Green's function (NEGF) simulation we look to investigate the effect of strain in MoS 2 armchair nanoribbon (ANR)-metal junctions. We consider a (10, 0) MoS 2 ANR and various metals as Ti, Cr, Al and Ag for contact material. The effect of strain both in plain and out of plain direction is considered. We calculated the work function variations, band-gaps and carrier effective masses with Density Functional Theory (DFT) calculation and evaluated the Schottky barriers with the Schottky-Mott formula. The currents through these barriers were then evaluated with NEGF calculations. Our results show a wide possibility of output current enhancement with Schottky barrier height modulation with the proper choice of strain and contact material combinations.

In this work, we investigate the layer dependency of Mos2channel material based Double Gate Schottky barrier MOSFET. In order to evaluate the transport properties due to this effect accurately, we have calculated the electronic properties of multilayer Mos2using density functional theory and incorporated those parameters in our analytical model for double Gate Schottky barrier MOSFET. A full description of the electron transport due to tunneling through the Schottky barrier and thermionic emission of electrons is computed in our model. Our results demonstrate that monolayer Mos2shows good device characteristics for logic applications, with ON/OFF ratio $\sim 10^{7}$ . As far as the layer dependency is concerned, more than two times higher drain current is achievable for the device made of the monolayer based channel than that of the five-layer based channel of Mos2. In Mos2, drive current, transconductance significantly reduced with increasing number of layer. The results obtained with our model concur with experimental reports.

The report focuses on an optimization scheme of advanced MOSFETs for designing power efficient circuits. For the purpose the physics-based compact model HiSIM2 is applied so that the relationship between device and circuit characteristics can be investigated properly. It is demonstrated that the short-channel effect, which is usually measured by the threshold-voltage shift compared to the long-channel MOSFET, provides the consistent measure as the short-channel effect on device performance degradation. However, the circuitry performances degradation such as the power loss cannot be predicted sufficiently by the short channel effect alone. It is demonstrated that the power efficient circuit design can be achieved by minimizing the additional leakage current caused by the short-channel contribution.

This paper presents a theoretical study of tunneling current density and the leakage current through multi-layer (stacked) trapping layer in the gate dielectric in MOS non-volatile memory devices. Two different 2D materials ($$\hbox {MoS}_{2}$$MoS2 and black phosphorous) with a combination of high-k dielectric ($$\hbox {HfO}_{2}$$HfO2) have been used for the study with differently ordered stacks i.e., as trapping layer and substrate. The material properties of 2D materials like density of states, effective mass and band structure has been evaluated using density functional theory simulations. Using the Maxwell---Garnett effective medium theory we have calculated the effective barrier height, effective bandgap, effective dielectric constant and effective mass of the gate dielectric stacks. By applying WKB approximation in the multi-layer trapping layer we have studied the effect of the direct and Fowler---Nordheim tunneling currents. The leakage current in all the different stack combinations used has also been evaluated. The results obtained have shown to match the required dynamics of a memory device.

We present a computational study on the impact of line defects on the electronic properties of monolayer MoS $_{2}$ . Four different kinds of line defects with Mo and S as the bridging atoms, consistent with recent theoretical and experimental observations, are considered herein. We employ the density functional tight-binding (DFTB) method with a Slater–Koster-type DFTB-CP2K basis set for evaluating the material properties of perfect and the various defective MoS $_{2}$ sheets. The transmission spectra are computed with a DFTB-non-equilibrium Green’s function formalism. We also perform a detailed analysis of the carrier transmission pathways under a small bias and investigate the phase of the transmission eigenstates of the defective MoS $_{2}$ sheets. Our simulations show a two to four fold decrease in carrier conductance of MoS $_{2}$ sheets in the presence of line defects as compared to that for the perfect sheet.

In this work the emerging 2 dimensional (2D) material ReS2 is studied for its performance as channel material in next generation deeper nanoscale MOSFET. Combining ab-initio material simulations and non-equilibrium Green's function (NEGF) based transport calculations, we studied monolayer ReS2 nMOS devices of 5, 10 and 15nm channel length. The 5nm ReS2 FET shows promise as logic device with drive currents of 235.1μA/μm, ON/OFF ratio of ∼104 and good DIBL suppression. The direct tunneling leakage issues were not found to be significant down to 5nm channel length.

In this work, we investigate the contact and channel material dependency of the transport properties of Siticene and Armchair CNT based heterostructure devices. The Density of States (DOS) of the heterojunction materials and transport properties like Device Density of States, transmission eigenstate, transmission pathway, transmission spectrum and I-V characteristics of two structures — CNT-Si-CNT and Si-CNT-Si are investigated. We see that CNT-Silicene-CNT heterojunction gives higher current and it is more conducive for FET device application. This device also shows better transport properties in terms of transmission Eigenstate, Transmission pathway and IV characteristics.

Magnetic tunnel junctions (MTJ) have emerged as a possible alternative to charge based data storage cells. With the development in 2-dimensional materials, non-conventional insulators like 2D hexagonal boron nitride (hBN), Ca(OH) 2 and Mg(OH) 2 have emerged as possible dielectrics in future nanoscale devices. Thus it could be interesting to investigate the application of these materials as insulators in MTJ devices. In this work, we have studied the effect of Ca(OH) 2 , hBN and Mg(OH)2 based composite oxides in a MTJ device. The barrier height of the composite oxide and effective mass of the same has been calculated using Maxwell-Garnett model. With the MTJ Lab tool available at nanohub, device characteristics were calculated. We have studied various MTJ parameters like parallel and anti-parallel resistance and differential resistance, tunnelling magneto resistance (TMR) and differential TMR (DTMR), and the variation of spin transfer torque (STT) components (In-Plane and Out-of-Plane STT) with voltage.

We report the effect of topological as well as lattice vacancy defects on the electro-thermal transport properties of the metallic zigzag graphene nano ribbons at their ballistic limit. We employ the density function theory---Non equilibrium green's function combination to calculate the transmission details. We then present an elaborated study considering the variation in the electrical current and the heat current transport with the change in temperature as well as the voltage gradient across the nano ribbons. The comparative analysis shows, that in the case of topological defects, such as the Stone-Wales defect, the electrical current transport is minimum. Besides, for the voltage gradient of 0.5 Volt and the temperature gradient of 300 K, the heat current transport reduces by $${\sim }62\,\%$$ ~ 62 % and $${\sim }50\,\%$$ ~ 50 % for the cases of Stones-Wales defect and lattice vacancy defect respectively, compared to that of the perfect one.

In this work from first-principles simulations we investigate bilayer van der Waals heterostructures (vdWh) of emerging 2-dimensional (2D) optical materials SnS 2 and SnSe 2 with monolayer InSe. With density functional theory (DFT) calculations, we study the structural, electronic, optical and carrier transport properties of the SnX 2 (X=S,Se)-InSe vdWh. Calculations show SnX 2 -InSe in its most stable stacking form (named AB-1) to be a material with a small (0.6- 0.7eV) indirect band-gap. The bilayer vdWh shows broad spectrum optical response, with number of peaks in the infra-red to visible region. In terms of carrier transport properties, asymmetry in conductance was observed with respect to the transport direction and electron and hole transmission. The findings are promising from the viewpoint of nanoelectronics and photonics., The following article has been submitted for peer-review. After it is published, it will be found at Link

In this paper we present an analytical study of Double Gate (DG) MOSFET memory devices with Si and Au nanocrystal embedded gate dielectric stacks. We considered an undoped long channel DG MOSFET, having a multilayer SiO2 (5 nm)–Si/Au nc embedded Si3N4 (6 nm)–SiO2 (7 nm) gate dielectric. From a quasi-1-D analytic solution of the Poisson equation, the potential and the electric fields in the substrate and the different layers of the gate oxide stack were derived. Thereafter following a trap-like model using the WKB approximation, we have investigated the Fowler Nordheim tunneling currents from the Si inversion layer to the embedded nanocrystal states in such devices. We evaluated the write-erase characteristics, gate tunneling currents, threshold voltage shifts and the output characteristics of the NVM devices from our analytical model. The performance of the nanoparticle embedded DGMOS memory device was compared with that of a DG SONOS NVM of similar dimensions. From the studies, the nc embedded devices showed better performance than the conventional SONOS DGMOS NVM. Among the two ncs compared the nc-Au embedded device emerged as the better performer in terms of higher charge density, faster charging, higher threshold voltage shift and better charge retention.

In this work we present an ab-initio study of electronic properties of 1 dimensional (1D) core-shell nanostructures made of MS2 (MoS2, WS2) or BN armchair nanotube encapsulated carbon nanotubes (CNT). With local density approximation (LDA) in density functional theory (DFT) we calculate the bandstructure, carrier effective masses, various fundamental electrostatic features and optical absorption in such core-shell tubes. The carrier transport in these structures are important for nanoelectronics applications and are studied with the Greens function formalism. Simulations show a moderate indirect band gap in the core-shell CNT@MS2 tubes while the CNT@BN shows metallic nature. The varying chirality of CNT strongly affects the carrier effective masses of the CNT@MS2 structure. Electron density is found to be much more localized near the atom cores and stronger in magnitude for the CNT@BN while the W atoms show a more prominent electron-gas presence around them than Mo atoms as found in the electron localization functions. In the CNT@MS2 systems the electrostatic difference potential indicates a drive to transfer charge from the metal to the S atoms in the shell. In terms of optical absorption a strong and sharper peak is observed around 6 eV for the CNT@BN compared to a more broad absorption spectra of the CNT@MS2. Metallic transmission spectra is seen for CNT@BN while CNT@MS2 shows non-metallic transport but with a larger number of transmission states near fermi level. The electronic and optical properties and its possible tuning in the core-shell structures can be useful in various applications such as shielded interconnects, logic switches and optoelectronics., 15 pages, 8 figures, 2 tables

In this work, we study the carrier transport properties of three non-graphitic armchair nanotubes (of Silicene, Germanene and Phosphorene) under an empirical tight binding (ETB)-non-equilibrium Green's function (NEGF) approach. The electronic properties are studied with extended Huckel theory, while phonon calculations are carried out with Stillinger-Weber classical potentials in ATK. The impact of Stone-Wales (SW) defects in electron and phonon transport properties of such tubes is also investigated. Our simulations show Silicene and Germanene nanotubes to offer much better electrical conduction than phosphorene NTs. The carrier transport and change charge density around the SW defect site is found to be affected more significantly in phosphorene nanotubes. Suppression of phonon transmission with introduction of defect is observed for all the cases. The overall results show a good possibility of defect engineered tailoring of electrical and thermal properties of these nanotubes.

Armchair nanotubes of MoS2 and WS2 offer a sizeable band gap, with the advantage of a one dimensional (1D) electronic material, but free from edge roughness and thermodynamic instability of nanoribbons. Use of such semiconducting MX2 (MoS2, WS2) armchair nanotubes (NTs) in conjunction with metallic carbon nanotubes (CNT) could prove useful for nanoelectronics and photonics applications. In this work atomistic simulations of MoS2 NT-CNT and WS2 NT-CNT junctions are carried out to study the physics of such junctions. With density functional theory (DFT) we study the carrier density distribution, effective potential, electron difference density, electron localization function, electrostatic difference potential and projected local density of states of such MX2 NT-CNT 1D junctions. Thereafter the conductance of such a junction under moderate bias is studied with non-equilibrium Greens function (NEGF) method. From the forward bias characteristics simulated from NEGF, we extract diode parameters of the junction. The electrostatic simulations from DFT show the formation of an inhomogeneous Schottky barrier with a tendency towards charge transfer from metal and chalcogen atoms towards the C atoms. For low bias conditions, the ideality factor was calculated to be 1.1322 for MoS2 NT-CNT junction and 1.2526 for the WS2 NT-CNT junction. The Schottky barrier heights displayed significant bias dependent modulation and are calculated to be in the range 0.697 - 0.664eV for MoS2 NT-CNT and 0.669-0.610 eV for the WS2 NT-CNT respectively., Comment: 13 pages 8 figures 1 table

A sol-gel derived ZnO-p-Si heterojunction structure were fabricated and investigated as a potential methane sensor. Three configurations with different contacts (Pd-Ag contact both on ZnO and Si / Pd-Ag on ZnO side and Au on Si / and Au on both sides of the junction) were fabricated in order to study the impact of the catalytic contact on the methane sensing properties. Structural characterization with high resolution FESEM and EDX study revealed the synthesis of highly crystalline ZnO thin film with particle size ~40nm. The catalytic contact metal used was also of nanoporous nature as was revealed from FESEM were as the noncatalyic metal showed flake like texture. The heterojunctions were investigated at different operating temperatures (50C300C) and at different operating voltages (1-5V) for varying concentrations of methane (0.1%, 0.5% and 1.0%). It was observed that the device with Pd-Ag (70%) contacts on both sides offered shorter response time (~28sec) and much higher response magnitude (~63%) compared to the sensor with Au contact both sides (response time ~47 sec and response magnitude ~ 19%). It is further revealed that the sensor performance with catalytic contact only to ZnO (and Au to Si) is almost the same as that of sensor having catalytic contact on both sides, emphasizing the fact that using catalytic contact to the sensing layer only modulates the sensor characteristics. The diode parameters like ideality factor, saturation current and the change in barrier height (upon exposure to methane) were also calculated for getting the insight of the sensing mechanism and were found to be in well agreement with the experimental results. KeywordsSol-gel, ZnO, Heterojunction devices, Methane sensor, Pd-Ag (70%) catalytic contact INTERNATIONAL JOURNAL ON SMART SENSING AND INTELLIGENT SYSTEMS VOL. 3, NO. 2, JUNE 2010

Here, we report the performance of vacancy affected supercell of a hybrid Graphene-Boron Nitride embedded armchair nanoribbon (a-GNR-BN) based n-MOSFET at its ballistic transport limit using Non Equilibrium Green's Function (NEGF) methodology. A supercell is made of the 3p configuration of armchair nanoribbon that is doped on the either side with 6 BN atoms and is also H-passivated. The type of vacancies studied are mono (B removal), di (B and N atom removal) and hole (removal of 6 atoms) formed all at the interface of carbon and BN atoms. Density Functional Theory (DFT) is employed to evaluate the material properties of this supercell like bandgap, effective mass and density of states (DOS). Further band gap and effective mass are utilized in self-consistent PoissonSchrodinger calculator formalized using NEGF approach. For all the vacancy defects, material properties show a decrease which is more significant for hole defects. This observation is consistent in the device characteristics as well where ON-current (ION ) and Sub Threshold Slope (SS) shows the maximum increment for hole vacancy and increase is more significant becomes when the number of defects increase., in 18th International Workshop on Computational Electronics (2015)

We investigate the effect of tensile and compressive strain in Phosphorene FET. Different percentage of tensile and compressive strain are applied on monolayer Phosphorene along the zigzag edge and the corresponding effects on bandgap, electron effective mass and ON current are analyzed. The optimum strain region is observed at 4% tensile strain for Phosphorene for the application in FET device. About 8.5 times improvement in ON current was observed for this strain percentage.

In this paper we show the effect of electron-phonon scattering on the performance of monolayer (1L) MoS2 and WSe2 channel based n-MOSFETs. Electronic properties of the channel materials are evaluated using the local density approximation (LDA) in density functional theory (DFT). For phonon dispersion we employ the small displacement / frozen phonon calculations in DFT. Thereafter using the non-equilibrium Green's function (NEGF) formalism, we study the effect of electron-phonon scattering and the contribution of various phonon modes on the performance of such devices. It is found that the performance of the WSe2 device is less impacted by phonon scattering, showing a ballisticity of 83% for 1L-WSe2 FET for channel length of 10 nm. Though 1L-MoS2 FET of similar dimension shows a lesser ballisticity of 75%. Also in the presence of scattering there exist a a 21-36% increase in the intrinsic delay time (tau) and a 10-18% reduction in peak transconductance (g(m)) for WSe2 and MoS2 devices respectively. (C) 2015 Author(s).

The term sensor comes from the Latin word ‘sentire’ which means to perceive (Sze in Semiconductor sensors. Wiley, New York, 1994 [1]). In electronics sensors are a type of devices that converts some non-electrical input parameter (which we want to measure) into electrical signals having some correlation with the magnitude and nature of the input. Sensors have invaded every sphere of modern industry. In industrial automation, consumer electronics, automobile, space-exploration, medical sector, sensors are everywhere. One of the chief applications of sensors is for the detection of gases and chemical vapors.

We present the effect of different stacking orders on carrier transport properties of multi-layer black phosphorous. We consider three different stacking orders AAA, ABA and ACA, with increasing number of layers (from 2 to 6 layers). We employ a hierarchical approach in density functional theory (DFT), with structural simulations performed with Generalized Gradient Approximation (GGA) and the bandstructure, carrier effective masses and optical properties evaluated with the Meta-Generalized Gradient Approximation (MGGA). The carrier transmission in the various black phosphorous sheets was carried out with the non-equilibrium Greens function (NEGF) approach. The results show that ACA stacking has the highest electron and hole transmission probabilities. The results show tunability for a wide range of band-gap, carrier effective masses and transmission with a great promise for lattice engineering (stacking order and layers) in black phosphorous., Comment: 18 Pages , 10 figures

The physics and structure of solid materials is an extremely vast and interesting field of study. In this chapter, we would only look at the basic concepts of solid-state physics, with an outlook toward nanocrystalline solids.

We live in a macroscopic world surrounded by macroscopic objects, which adhere to the laws of classical mechanics and are very comfortable with it. From the trajectory of a humble pebble thrown into a pond and the ripples thus created by it, to the motion of the great planets can all be quite satisfactorily explained within the domain of classical physics. However, apart from this macroscopic scale, there exist numerous other phenomena around us, especially on the microscopic scale, which seem to defy most conventional “common-sense” beliefs. The key to the understanding of the workings of this amazing microscopic world lies with quantum physics.

We present a computational study on the impact of tensile/compressive uniaxial ($\varepsilon_{xx}$) and biaxial ($\varepsilon_{xx}=\varepsilon_{yy}$) strain on monolayer MoS$_{2}$ NMOS and PMOS FETs. The material properties like band structure, carrier effective mass and the multi-band Hamiltonian of the channel, are evaluated using the Density Functional Theory (DFT). Using these parameters, self-consistent Poisson-Schr\"{o}dinger solution under the Non-Equilibrium Green's Function (NEGF) formalism is carried out to simulate the MOS device characteristics. 1.75$%$ uniaxial tensile strain is found to provide a minor (6$%$) ON current improvement for the NMOSFET, whereas same amount of biaxial tensile strain is found to considerably improve the PMOSFET ON currents by 2-3 times. Compressive strain however degrades both NMOS and PMOS device performance. It is also observed that the improvement in PMOSFET can be attained only when the channel material becomes indirect-gap in nature. We further study the performance degradation in the quasi-ballistic long channel regime using a projected current method.

Gate All Around (GAA) MOSFET Non Volatile Memories (NVMs) are a recent topic of research. Such devices usually employ the conventional Si-Oxide-Nitride-Si (SONOS) stacks for charge storage. However, embedding nanocrystals (nc) in the gate dielectric could be highly useful in improving charge storage and suppressing charge leakage in such GAA memories. In this work, we compare the performance of the nc Au embedded SiO 2 -HfO 2 stacked gate dielectric GAA NVM with an Oxide-Nitride-Oxide (ONO) stack GAA NVM device of similar dimensions. Using a pseudo 2D based method, we evaluate the surface potential of the GAA MOS. Applying the Gauss' law the fields in the different layers in the gate dielectric stacks of the GAA MOS device was evaluated. Thereafter using a Wentzel-Kramers-Brillouin (WKB) approximation based model, we compute the Fowler-Nordheim tunneling currents in a GAA MOSFET NVM. We simulated the Ig-Vg characteristic, flatband shifts and memory window, and the direct tunneling leakage in such devices.

In this work, we present an analytical model for studying the sub-threshold charge leakage in nanocrystal embedded gate dielectric DGMOSFET Non Volatile Memories. From a parabolic approximation based method, we evaluate the surface potential and the threshold voltage in such a device. Thereafter using the WKB approximation, the charge leakage from the nanocrystal layer to the Si substrate under sub-threshold condition by the direct tunneling (DT) mechanism was modeled. We also model the lateral diffusion suppression in such DGMOS NVMs, and the impact of the nanocrystal embedding density on lateral diffusion.