Dataset Information

Fabrication of WS₂/GaN p-n Junction by Wafer-Scale WS₂ Thin Film Transfer.

ABSTRACT: High quality wafer-scale free-standing WS₂ grown by van der Waals rheotaxy (vdWR) using Ni as a texture promoting layer is reported. The microstructure of vdWR grown WS₂ was significantly modified from mixture of crystallites with their c-axes both parallel to (type I) and perpendicular to (type II) the substrate to large type II crystallites. Wafer-scale transfer of vdWR grown WS₂ onto different substrates by an etching-free technique was demonstrated for the first time that utilized the hydrophobic property of WS₂ and hydrophilic property of sapphire. Our results show that vdWR is a reliable technique to obtain type-II textured crystallites in WS₂, which is the key factor for the wafer-scale etching-free transfer. The transferred films were found to be free of observable wrinkles, cracks, or polymer residues. High quality p-n junctions fabricated by room-temperature transfer of the p-type WS₂ onto an n-type GaN was demonstrated with a small leakage current density of 29.6??A/cm² at -1?V which shows superior performances compared to the directly grown WS₂/GaN heterojunctions.

SUBMITTER: Yu Y

PROVIDER: S-EPMC5126671 | biostudies-literature | 2016 Nov

REPOSITORIES: biostudies-literature

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Publications

Fabrication of WS2/GaN p-n Junction by Wafer-Scale WS2 Thin Film Transfer.

Yu Yang Y Fong Patrick W K PW Wang Shifeng S Surya Charles C

Scientific reports 20161129

High quality wafer-scale free-standing WS2 grown by van der Waals rheotaxy (vdWR) using Ni as a texture promoting layer is reported. The microstructure of vdWR grown WS2 was significantly modified from mixture of crystallites with their c-axes both parallel to (type I) and perpendicular to (type II) the substrate to large type II crystallites. Wafer-scale transfer of vdWR grown WS2 onto different substrates by an etching-free technique was demonstrated for the fi ...[more]

PMID: 27897210

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Project description:A wafer scale bulge testing system has been constructed to study the mechanical properties of thin films and microstructures. The custom built test stage was coupled with a pressure regulation system and optical profilometer which gives high accuracy three-dimensional topographic images collected on the time scale of seconds. Membrane deflection measurements can be made on the wafer scale (50-150 mm) with up to nanometer-scale vertical resolution. Gauge pressures up to 689 kPa (100 psi) are controlled using an electronic regulator with and accuracy of approximately 0.344 kPa (0.05 psi). Initial testing was performed on square diaphragms 350, 550, and 1200 microm in width comprised of 720+/-10 nm thick low pressure chemical vapor deposited silicon nitride with approximately 20 nm of e-beam evaporated aluminum. These initial experiments were focused on measuring the system limitations and used to determine what range of deflections and pressures can be accurately measured and controlled. Gauge pressures from 0 to approximately 8.3 kPa (1.2 psi) were initially applied to the bottom side of the diaphragms and their deflection was subsequently measured. The overall pressure resolution of the system is good (approximately 350 Pa) but small fluctuations existed at pressures below 5 kPa leading to a larger standard deviation between deflection measurements. Analytical calculations and computed finite element analysis deflections closely matched those empirically measured. Using an analytical solution that relates pressure deflection data for the square diaphragms the Young's modulus was estimated for the films assuming a Poisson's ratio of v=0.25. Calculations to determine Young's modulus for the smaller diaphragms proved difficult because the pressure deflection relationship remained in the linear regime over the tested pressure range. Hence, the calculations result in large error when used to estimate the Young's modulus for the smaller membranes. The deflection measurements of three 1200 x 1200 microm(2) Si(3)N(4-x) membranes were taken at increased pressures (>25 kPa) to increase nonlinearity and better determine Young's modulus. This pressure-deflection data were fit to an analytical solution and Young's modulus estimated to be 257+/-3 GPa, close to those previously reported in literature.

Dataset Information

Fabrication of WS₂/GaN p-n Junction by Wafer-Scale WS₂ Thin Film Transfer.

Publications

Fabrication of WS<sub>2</sub>/GaN p-n Junction by Wafer-Scale WS<sub>2</sub> Thin Film Transfer.

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