Van der Pauw method

About: Van der Pauw method is a research topic. Over the lifetime, 1682 publications have been published within this topic receiving 25364 citations.

Substrate effect on the transport properties of semiconducting films

Abstract: In this study, transport properties of InP/Si heteroepitaxial layers were investigated. Current‐voltage characteristics, measured across the heterointerface, revealed diode behavior at 300 K only with Si of p‐type conductivity. With n‐type Si, a transition from Ohmic behavior at 300 K to a diode characteristic at low temperatures was observed at 250 K. Due to the efficient electrical isolation of layer and p‐type substrate van der Pauw measurements with InP/p‐Si could be analyzed in the conventional manner. For InP/n‐type Si the applicability of the two‐layer conduction model suggested by Petritz could be demonstrated for 300 K measurements. With decreasing temperature a pronounced deviation from the model occurred due to the increased effect of the heterointerface.

Improved opto-electrical properties of spray deposited ytterbium doped cadmium oxide thin films

Abstract: Transparent conducting metal oxides (TCOs) associate the properties of high optical transparency and electrical conductivity, which makes them suitable for variety of applications such as window layer in liquid crystal and electroluminescent display devices as well as in solar cells. Among different TCO’s, cadmium oxide (CdO) has received tremendous attention as a potential alternative to Sn-doped In2O3 (ITO) due to its high intrinsic dopability coupled with outstanding mobility and high electrical conductivity. In the present study, for first time the doping of ytterbium (Yb) into CdO films prepared using a simple and effective spray pyrolysis technique demonstrated. The structural, morphological and optoelectronic properties of Yb doped CdO thin films as a function of Yb concentration (1–3 at.%) have been studied. X-ray diffraction, field-emission scanning electron microscopy, X-ray photoelectron spectroscopy, optical absorption spectroscopy, luminescence measurements and for electrical properties Hall effect set up in van der Pauw configuration have been employed to study the properties of Yb-doped CdO thin films. Yb doped CdO thin films exhibit excellent optical transparency, with an average transmittance over 75% in the visible region. It is found that Yb doping widens the optical band gap from 2.63 to 2.88 eV, via a Moss–Burstein shift and further decreases to 2.77 eV. The maximum reflectivity of 97.24% achieved for 2.5 at.% Yb:CdO film. The better values of resistivity, carrier concentration, mobility and figure of merit have been obtained for 2.5 at.% Yb:CdO, which are 2.6 × 10−4 Ω cm, 13.9 × 1020 cm−3, 17.39 cm2/Vs and 45.87 × 10−3 (Ω)−1 respectively. The obtained results revealed that Yb dopant has a significant influence on the optoelectronic properties of CdO-based TCO compound.

DC Magnetron-Sputtered Mo Thin Films with High Adhesion, Conductivity and Reflectance

Abstract: The main challenge in the deposition of molybdenum thin films for high efficiency in copper indium gallium selenide (CIGS) modules lies in gaining an adherent coating without compromising conductivity and reflectance characteristics. In this study, Mo thin films were deposited on soda-lime glass by DC magnetron sputtering at different deposition power (55, 100, 200 and 300 W) and with high working gas pressure (2 and 4 Pa). Analytical techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and Hall effect were employed to analyze the structure, morphology and electrical resistivity of the deposited films. Ultraviolet–visible (UV–Vis) spectrometry was performed to measure the reflectance and a cross-hatch adhesion tape test was employed to determine the adhesion behavior of deposited films. With higher sputtering power and reduced gas pressure, an increase in the crystallite size of the deposited films was observed. Films deposited at higher gas pressure were found with tensile stresses and higher adhesion with the substrate. The van der Pauw method reveals an increase in conductivity at high power and low gas pressure. Improved reflectance was achieved at moderate sputtering power and low gas pressure.

Effect of laser annealing on electrical and optical properties of n‐mercury cadmium telluride

Abstract: Single crystals of n‐Hg1−xCdxTe (x=0.18) were grown by the Bridgman technique. The bulk single crystals were irradiated with laser pulses of various energy densities. A pulsed laser (Nd:YAG) capable of producing 10‐ns pulses of 0.53‐μm wavelength (frequency doubled) with varying energy densities (2–50 mJ/cm2) was employed. dc conductivity and Hall coefficient measurements were made on the single crystal using the van der Pauw technique in the temperature range 77–300 K, for both as‐grown and laser‐irradiated samples. Also, transmission measurements of the samples were taken at room temperature. Both electrical and optical studies showed that laser irradiation introduces additional defects in mercury cadmium telluride (MCT), and its quality deteriorates instead of improving as observed in many other semiconductor materials. We found that laser irradiation increases free‐carrier concentration and decreases the band gap of MCT.