arXiv subjects

Badri Vishal

Publications and source records attributed to Badri Vishal.

4 recordsLinked to original sources

arXiv2023

Impact of TCO Microstructure on the Electronic Properties of Carbazole-based Self-Assembled Monolayers

Carbazole-based self-assembled monolayers (PACz-SAMs), anchored via their phosphonic acid group on a transparent conductive oxide (TCO) have demonstrated excellent performance as hole-selective layers in inverted perovskite solar cells. However, the influence of the TCO microstructure on the work function (WF) shift after SAM anchoring as well as the WF variations at the micro/nanoscale have not been extensively studied yet. Herein, we investigate the effect of the Sn-doped In2O3 (ITO) microstructure on the WF distribution upon 2PACz-SAMs and NiOx/2PACz-SAMs application. For this, ITO substrates with amorphous and polycrystalline (featuring either nanoscale or microscale-sized grains) microstructures are studied. A correlation between the ITO grain orientation and 2PACz-SAMs local potential distribution was found via Kelvin probe force microscopy and electron backscatter diffraction. These variations vanish for amorphous ITO or when adding an amorphous NiOx buffer layer, where a homogeneous surface potential distribution is mapped. Ultraviolet photoelectron spectroscopy confirmed the ITO WF increase after 2PACz-SAMs deposition. Considering the importance of polycrystalline TCOs as high mobility and broadband transparent electrodes, we provide insights to ensure uniform WF distribution upon application of hole transport SAMs, which is critical towards enhanced device performance.

cond-mat.mtrl-sci↗

arXiv2020

Heterostructures of hetero-stack of 2D TMDs (MoS2, WS2 and ReS2) and BN

In this manuscript, we describe optical emission of heterostructure of hetero-stack between 2D TMDs (MoS2, WS2, and ReS2) and BN. Similar to our previous results on the stack of similar type of TMDs, intense PL emission peak is observed around 2.13 eV but is split around 2.13eV into two or more peaks depending on the different stack of TMDs with BN. The transitions from the valence band of BN to conduction bands of different TMD stacks due to quantum coupling and specific orientation explain the strong peak in the PL spectra.

cond-mat.mtrl-sci↗

arXiv2018

Chemically stabilized epitaxial wurtzite-BN thin film

We report on the chemically stabilized epitaxial w-BN thin film grown on c-plane sapphire by pulsed laser deposition under slow kinetic condition. Traces of no other allotropes such as cubic (c) or hexagonal (h) BN phases are present. Sapphire substrate plays a significant role in stabilizing the metastable w-BN from h-BN target under unusual PLD growth condition involving low temperature and pressure and is explained based on density functional theory calculation. The hardness and the elastic modulus of the w-BN film are 37 & 339 GPa, respectively measured by indentation along <0001> direction. The results are extremely promising in advancing the microelectronic and mechanical tooling industry.

cond-mat.mtrl-sci↗

arXiv2016

Substrate induced tuning of compressive strain and phonon modes in large area MoS2 and WS2 van der Waals epitaxial thin films

Large area MoS2 and WS2 van der Waals epitaxial thin films with complete control over number of layers including monolayer is grown by pulsed laser deposition utilizing slower growth kinetics. The films grown on c-plane sapphire show stiffening of A1g and E12g phonon modes with decreasing number of layers for both MoS2 and WS2. The observed stiffening translate into the compressive strain of 0.52 % & 0.53 % with accompanying increase in fundamental direct band gap to 1.74 and 1.68 eV for monolayer MoS2 and WS2, respectively. The strain decays with the number of layers. HRTEM imaging directly reveals the nature of atomic registry of van der Waals layers with the substrate and the associated compressive strain. The results demonstrate a practical route to stabilize and engineer strain for this class of material over large area device fabrication.

cond-mat.mtrl-sci↗