Sanjay Behura

San Diego State University | SDSU · Department of Physics

Ultra-smooth hexagonal boron nitride (h-BN) can dramatically enhance the carrier/phonon transport in interfaced transition metal dichalcogenides (TMDs), and amplify the effect of quantum capacitance in field-effect gating. All the current processes to realize h-BN-based heterostructures involve transfer or exfoliation. Rational chemistries and proc...

Electronic coupling of graphene atop a bulk semiconductor and the resultant interfacial energy-band reorganization create a light-sensitive junction only one atom below the front surface. Uniquely, this architecture leads to the surface being in extremely close proximity to the depletion region (typically buried several micrometres under the surfac...

Artificial moiré superlattices are formed by vertically stacking two monolayers of two-dimensional (2D) materials and rotating one of the layers with a finite twist angle. The resultant moiré pattern in the twisted heterostructures exhibits periodic length scale larger than that of lattice atoms of the individual layers. Furthermore, the moiré patt...

Hexagonal boron nitride (h-BN) and its heterostructures with graphene are widely investigated van der Waals (vdW) quantum materials for electronics, photonics, sensing, and energy storage/transduction. However, their metal catalyst-based growth and transfer-based heterostructure assembly approaches present impediments to obtaining high-quality and...

Understanding the optothermal physics of quantum materials will enable the efficient design of next-generation photonic and superconducting circuits. Anharmonic phonon dynamics is central to strongly interacting optothermal physics. This is because the pressure of a gas of anharmonic phonons is temperature dependent. Phonon-phonon and electron-phon...

Important topics include nanomanufacturing of high-performance piezoelectric nanogenerators for energy harvesting, nanosensor, nanorobots, nanomedicine, nano diagnostic tools, 3D nano printing, additive nanomanufacturing of functional materials for human‐integrated smart wearables, and nanofabrication techniques. Nanomanufacturing and Nanomaterials...

The book discuss of the design and fabrication of nano- and micro-devices in a comprehensive manner.

Nanomanufacturing involves fabricating nanoscale components or materials and integrating their features as well as their resolution into systems that are engineered as desired. It is possible to achieve novel characteristics, features and functionalities in nanoscale manufacturing with utmost precision and control in the nature of processes as well...

Methyl ammonium lead iodide (MAPbI3) degrades with light exposure, thus modifying the intrinsic properties. Herein, we studied the diatomic vibrations in hexagonal boron nitride (h-BN)/MAPbI3 to preserve MAPbI3 stability. A thin layer of h-BN created dipole-barriers for iodine to prevent ion migration through the lattice. The simple Harmonic Oscill...

Piezoelectric energy harvester has attracted considerable attention as an independent power source for applications in biocompatible, implantable, and flexible electronic devices. However, the lacuna of getting enhanced piezoelectric response from flexible lead-free polymer-based composite persists in this field. Here, we present a detailed study o...

Transition-metal oxides such as cupric and cuprous oxides are strongly correlated materials made of earth-abundant chemical elements displaying energy band gaps of around 1.2 and 2.1 eV. The ability to design nanostructures of cupric and cuprous oxide semiconductors with in situ phase change and morphological transition will benefit several applica...

Naturally-sensitized photoanodes in dye-sensitized solar cells (DSSCs) are promising alternatives to enhance photoabsorption, electron excitation/injection, but voltage loss remains a challenge. Here, we focus on understanding the cascading of energy levels in perovskite semiconductor cosensitized naturally-sensitized photoanodes to leverage forwar...

MXenes, represented by Mn+1XnTx, are an emerging class of two-dimensional (2D) nitrides, carbides and carbonitrides (X) of transition elements (M) containing terminations of free surface-active groups (T). These are derived by selective etching out ‘A’ from their corresponding MAX phases. MXene, like their other 2D material counterparts, has except...

Recent studies of the high energy-conversion efficiency of nanofluidic platform have revealed the enormous potential for efficient exploitation of electrokinetic phenomena in nanoporous membranes for clean-energy harvesting from salinity gradients. Here, we present nano-fluidic RED (NF-RED) device consisting of rationally designed vertically aligne...

With escalating global population, increased consumption of fossil fuels, spiralling energy demand, rapid environmental degradation and global climate change, energy and environmental issues are receiving considerable attention worldwide from the purview of sustainable development. In order to address these complex and interlinked challenges, the d...

Nanomaterials are the materials between 1 and few hundred nanometers in the size. Owing to the large surface to volume ratio and quantum confinement effects, nanomaterials have unique physical, chemical, optical, electrical, magnetic, thermal, mechanical, and acoustic properties as compared to their bulk counterpart. There are numerous literatures...

Two-dimensional (2D) van derWaals layered materials created new avenue for the last decade in the field of optoelectronics for showing promising new and diverse applications. Strong light-matter interaction properties on these materials in single to few atomic layer form realized promising thinnest possible photovoltaic solar cells. Over the past f...

Interfacing two-dimensional graphene oxide (2D GO) platelets with one-dimensional zinc oxide nanorods (1D ZnO) would create mixed-dimensional heterostructures suitable for modern optoelectronic devices. However, there remains a lack in understanding of interfacial chemistry and wettability in GO-coated-ZnO nanorod heterostructures. Here, we propose...

Dye-sensitized solar cells based on bacterial-based photosensitizers (bio-sensitized DSSCs) are promising bio-photoelectronic molecular devices exhibiting enhanced electron excitation, injection, and dye regeneration for efficient photon-to-electron quantum-conversion. Achieving high DSSCs performance via environmentally sustainable , cost-effectiv...

Titanium (Ti)-based halide perovskites with A 2 TiX 6 and ATiX 3 stoichiometry can be promising alternatives to lead-based perovskites due to their high cuboctahedral stability and reduced internal stresses. It is important to study compositional stability and crystal chemistry controlling the formation of BX 6 octahedral periodic arrays in Ti-base...

Controlling the doping levels in graphene by modifying the electric potential of interfaced nanostructures is important to understand "cascaded-doping"-based applications of graphene. However, graphene does not have active sites for nanoparticle attachment, and covalently adding functional groups on graphene disrupts its planar sp2-hybridization, a...

Application of the abundant salinity-gradients in the environment, motivated by the Gibbs free energy of mixing fresh and salt water, has been under intensive investigation for clean-energy harvesting. Globally, there is a potential of at least 2.6 TW of power that could be generated at coastal estuaries from the ion-concentration gradient. Recent...

The Van Hove singularity (VHS) induced enhancement of visible-frequency-absorption in atomically-thin two-dimensional (2D) crystals provides an opportunity for improved light management in photovoltaics; however, it requires the 2D nanomaterial to be in close vicinity to a photojunction. In this report, we design a Schottky junction-based photovolt...

Graphene intrinsically hosts charge carriers with ultra-high mobility and possesses a high quantum capacitance, which are attractive attributes for nanoelectronic applications requiring graphene-on-substrate base-architecture. Most of the current techniques for graphene production rely on the growth on metal catalyst surfaces, followed by a contami...

[Best Poster Award]

Binding graphene with auxiliary nanoparticles for plasmonics, photovoltaics, and/or optoelectronics, while retaining the trigonal-planar bonding of sp2 hybridized carbons to maintain its carrier-mobility has remained a challenge. The conventional nanoparticle-incorporation route for graphene is to create nucleation/attachment sites via ‘carbon-cent...

Hexagonal boron nitride (h-BN) is an ideal platform for interfacing with two-dimensional (2D) nanomaterials to reduce carrier scattering for high-quality 2D electronics. However, scalable, transfer-free growth of hexagonal boron nitride (h-BN) remains a challenge. Currently, h-BN based 2D heterostructures require exfoliation or chemical transfer of...

With the layer-dependent tunability of their optical band gap in the near-infrared (IR ) to visible spectrum, transition metal dichalcogenides (TMDs), including molybdenum disulfide (MoS2) and tungsten disulfide (WS2), exhibit strong light–matter interactions, making them suitable as absorber layers for optoelectronic devices. Currently, the WS2-ba...

Curvature induced dipole moment and orbital rehybridization in graphene wrinkles modify its electrical properties and induces transport-anisotropy. Current wrinkling processes are based on contraction of the entire substrate, and do not produce confined or directed wrinkles. Here we show that selective desiccation of bacterium under impermeable and...

Recent investigations involving nanoscale energy conversion using two-dimensional nanomaterials (2DNs) such as graphene, transition metal dichalcogenides (TMDs) holds promise to mitigate future energy challenges. The heterojunction devices designed by interfacing 2D layers with 3D bulk semiconductors (2D/3D heterojunctions) including graphene/silic...

Horizontally and vertically oriented few-layer graphenes have been synthesized directly on SiO2 coated Si substrates via thermal and hot-filament chemical vapor deposition, respectively. The effect of the direction of mass flow on the fabrication of graphene film is analysed and a plausible mechanism is proposed. The graphene/p-Si heterojunction is...

Understanding the physics of charge carrier transport at graphene/p-GaN interface is critical for achieving efficient device functionality. Currently, the graphene/p-GaN interface is being explored as light emitting diodes, however this interface can be probed as a potential photovoltaic cell. We report the intimate interfacing of mechanically exfo...

Percolating network of mixed 2D nanomaterials (2DNs) can potentially leverage the unique electronic structures of different 2DNs, their interfacial doping, manipulable conduction pathways and local traps. Here, we report on the percolation mechanism and electro-capacitive transport pathways of mixed-platelet network of hexagonal boron nitride (hBN)...

Chemical vapor deposition (CVD) growth of graphene on polycrystalline copper (Cu) foil in a low pressure conditions has been presented, aiming to achieve the highest quality with large-scale fabrications, which requires comprehensive understanding and effective controlling of the growth process. Herein, few-layer graphene (FLG) films with large-dom...

The effect of indium compositional grading on the performance of p-GaN/i-InxGa1-xN/n-GaN solar cell has been investigated using TCAD Silvaco. An enhancement in efficiency of almost two times is found and this may be due to the increase in short circuit current density and open circuit voltage. This can be imputed to high carrier collection due to t...

Structural isomers, graphene and boron nitride (BN), are logical materials for two-dimensional heterostructures with properties controllable via interfacial, structural, compositional and chemical modifications. These heterostructures can leverage the combination of graphene’s ultrahigh carrier-mobility, ultrafast photodetection, sensitivity, tunab...

Mechanically robust and flexible polymer-multiwall carbon nanotubes (MWCNT) composites are developed by in situ polymerization technique, where MWCNT are embedded in nontoxic, bio-compatible acryl amidebased polymer matrix. The addition of glycerol in the composite imparts required flexibility and a further addition of poly (3,4-ethylenedioxythiop...

Controlled nondegenerate doping of 2D semiconductors (2DSs) with their ultra-confined carriers, high quantum capacitance, and surface-sensitive electronics can enable tuning their Fermi level for rational device design. However, doping techniques for 3D semiconductors, such as ion-implantation cannot be directly applied to 2DSs, since they inflict...

The photovoltaic behaviour of metal/n-InGaN Schottky junction solar cells with low- and high-level injection conditions are explored by using voltage model. Four metals Ni–Au, Ni, Au and Pt are used as Schottky contact with n-InGaN and Schottky junction solar cell studied for open-circuit voltage (V oc) and short circuit current density (J sc) with...

Fabricated bi-layer graphene (BLG) has been studied as transparent and current spreading electrode (TCSE) for silicon solar cell, using TCAD-Silvaco 2D simulation. We have carried out comparative study using both Ag grids and BLG as current spreading electrode (CSE) and TCSE, respectively. Our study reveals that BLG based solar cell shows better ef...

A new process has been developed to grow silicon (Si) nanowires (NWs) and their growth mechanisms were explored and discussed. In this process, SiNWs were synthesized by simply oxidizing and then reducing Si wafers in a high temperature furnace. The process involves H2, in an inert atmosphere, reacts with thermally grown SiO2 on Si at 1100 oC enhan...

Chemically-derived graphene have been synthesized by modified Hummers method and reduced using sodium borohydride. To explore the potential for photovoltaic applications, graphene/p-silicon (Si) heterojunction devices were fabricated using a simple and cost effective technique called spin coating. The SEM analysis shows the formation of graphene ox...

High quality graphene film is fabricated using mechanical exfoliation of highly-oriented pyrolytic graphite. The graphene films on glass substrates are characterized using field-emission scanning electron microscopy, atomic force microscopy, Raman spectroscopy, UV-vis spectroscopy and Fourier transform infrared spectroscopy. A very high intensity r...

Disperse Multiwall carbon nanotubes (MWCNTs) are incorporated aqueous N-hydroxy methyl acrylamide, which is subjected to crosslinking to develop a transparent conductive composite free standing film. The effects of the concentration of MWCNTs and temperature on optical and electrical properties of nano-composites are investigated. Interestingly, on...

Experimental and theoretical investigations on the heterojunction of silicon (Si) with chemically derived graphene have been presented. The stability study of graphene oxide and reduced graphene oxide (rGO) in aqueous medium were performed by visual observation and surface charge measurement. The detailed characterization by FT-IR, UV–Vis, and Rama...

We report on the synthesis of large-domain graphene films on Cu metal substrates using hot-filament chemical vapor deposition (CVD). The intensity ratio between G and 2D-band is ~ 0.7 and the full-width at half maximum of 2D-band is 55 cm-1, indicating the formation of few-layer graphene films on Cu surface. The importance of this study is the use...

Using the fundamental models for voltage and current, we report on the photovoltaic behavior of graphene-on-semiconductor-based devices. The graphene-n-Si and graphene-n-GaAs systems are studied for open-circuit voltage (V OC) and short-circuit current density (J SC) under low- and high-level injection conditions. The effects of semiconductor dopin...

We report the fabrication of multiple layer graphene films on Cu coated SiO2/Si substrate using an in-house developed hot-filament chemical vapor deposition reactor, which relies on vertical mass flow with respect to the substrate configuration. Scanning electron microscopy, atomic force microscopy and Raman spectroscopy were used to characterize t...

Field emission from flat graphene sheets is a challenge due to fewer emission sites. Here, we have synthesized free-standing vertically oriented few-layer graphene (FLG) films directly on dielectric substrates by hot-filament chemical vapor deposition (HFCVD) without any catalyst or special substrate treatment. The fabricated FLGs with a large smoo...

We report on the 2D simulation of the heterojunction-based M/InxGa1-xN/GaN/M Schottky junction solar cell and studied the variations of different factors such as indium mole fraction, thickness, temperature and doping density of the n-InxGa1-xN active layer on the solar cell performance. The current–voltage characteristics have been simulated at va...

High quality, bi-layer graphene is fabricated using mechanical exfoliation of highly ordered pyrolytic graphite. The bi-layer graphene on the glass substrate is characterized using scanning electron microscopy, optical microscopy, micro-Raman spectroscopy and UV-vis spectrophotometer. The effects of substrate cleaning on the quality of graphene are...

In this work we have evaluated the open-circuit voltage developed across a metal/n-InGaN Schottky junction solar cells through both analytical and computer simulation as a function of varying indium composition. Our study includes four different systems such as Au/n-InGaN/Al, Pd/n-InGaN/Al, Ni/n-InGaN/Al and Pt/n-InGaN/Al with a variation of Indium...

The cut-off of Schottky behaviour for Indium Gallium Nitride (InxGa1-xN) Schottky junction solar cell (Metal/n- InGaN) as a function of indium composition for four metals - gold (Au), palladium (Pd), platinum (Pt) and nickel (Ni) is calculated through an analytical approach. The indium composition cut-off is calculated considering low level injecti...

The open-circuit voltage developed across a Schottky-Barrier (SB) solar cell was theoretically modeled to estimate it under high level injection conditions. An Open circuit voltage (Voc) of 0.709 V was obtained for specific metal/n-Si SB solar cell. A substantial increase of 42.6 % in Voc was noticed while comparing our result with that previously...

The open-circuit voltage, Voc developed across a Schottky-barrier (SB) solar cell has been modeled and calculated under low and high level injection conditions. The model predicted an increase of 42% in Voc in a metal/n-Si Schottky-barrier solar cell under high level injection condition, as compared to the low level injection condition while the SB...

Solid oxide fuel cells (SOFC), with its ability to use hydrocarbon fuels and capability to offer highest efficiency, have attracted great attention in India in recent years as an alternative energy generation system for future. But a great deal of problems associated with SOFC is needed to be solved before it can find commercial application. The re...