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.

Influence of oxygen argon ratio on the structural, electrical, optical and thermoelectrical properties of Al-doped ZnO thin films

Abstract: In this study, high quality of Al-doped ZnO (AZO) thin films were deposited at different oxygen argon ratio by direct current (DC) reactive magnetron sputtering using a Zn target (99.99%) containing Al of 1.5%. The obtained films were characterized and analyzed by X-ray diffraction (XRD) and ultraviolet–visible and infrared light spectrophotometer. The electrical properties had been investigated by van der Pauw method. It was also found that oxygen argon (O 2 /Ar) ratio had great influence on the properties. The results show that AZO thin films are polycrystalline with a preferred (0 0 2) orientation. The film stress increases with increasing O 2 /Ar ratio. The lowest resistivity of 1.306×10 −3 Ω cm was obtained for the AZO thin films prepared at O 2 /Ar ratio of 0.3/27. Hall mobility decreases with increasing the O 2 /Ar ratio. With increasing O 2 /Ar ratio, the transmittance of the AZO thin films has no evident changes. There is a strong absorption in the ultraviolet region. The optical absorption edge is found to shift to the longer wavelength with the increase of O 2 /Ar ratio. The measurements show that there is a striking Seebeck effect in the AZO thin films, and their thermoelectromotive force is linearly increased with increasing temperature difference (Δ T ). With increasing O 2 /Ar ratio and resistance of samples, thermoelectric power (TEP) decreases.

Modification of electrical and optical properties of CuO thin films by Ni doping

Abstract: Undoped and Ni-doped CuO thin films were deposited onto glass substrates using a spin-coating technique at different doping concentrations (undoped, 2, 4, 6, and 10 %). X-ray diffraction patterns for undoped and Ni-doped CuO thin films indicated that the films were polycrystalline, with preferential growth in the (002), (111), and (−311) directions. Atomic force microscopy images revealed that the surface morphologies of the films were not uniform. Scanning electron microscopy images confirmed the presence of agglomerated particles on the surfaces; the coverage increased with the doping level. A Hall effect system with a van der Pauw configuration was used to investigate the electrical properties of the CuO films. The free charge carrier concentration decreased and hole mobility increased with increasing Ni concentration, with the exception of the 10 % Ni-doped CuO sample. Ultraviolet–visible spectroscopy measurements of the film samples indicated an average transmittance of 30–40 % in the visible range. The optical band gap decreased slightly for low-level doping and increased from 2.03 to 2.22 eV for 10 % Ni incorporation. The electrical and optical properties of the CuO films were modified by Ni doping, i.e. the band gap decreased and the mobility increased almost linearly, with the exception of the 10 % Ni-doped sample. SEM images of a undoped b 2 % c 4 % d 6 %, and e 10 % Ni-doped CuO thin films.

Micro-four-point Probe Hall effect Measurement method

Abstract: We report a new microscale Hall effect measurement method for characterization of semiconductor thin films without need for conventional Hall effect geometries and metal contact pads We derive the electrostatic potential resulting from current flow in a conductive filamentary sheet with insulating barriers and with a magnetic field applied normal to the plane of the sheet Based on this potential, analytical expressions for the measured four-point resistance in presence of a magnetic field are derived for several simple sample geometries We show how the sheet resistance and Hall effect contributions may be separated using dual configuration measurements The method differs from conventional van der Pauw measurements since the probe pins are placed in the interior of the sample region, not just on the perimeter We experimentally verify the method by micro-four-point probe measurements on ultrashallow junctions in silicon and germanium On a cleaved silicon ultrashallow junction sample we determine carrier mobility, sheet carrier density, and sheet resistance from micro-four-point probe measurements under various experimental conditions, and show with these conditions reproducibility within less than 15%

LPCVD homoepitaxy of Si doped β-Ga2O3 thin films on (010) and (001) substrates

Abstract: This paper presents the homoepitaxy of Si-doped β-Ga2O3 thin films on semi-insulating (010) and (001) Ga2O3 substrates via low pressure chemical vapor deposition with a growth rate of ≥1 μm/h. Both high resolution scanning transmission electron microscopy and X-ray diffraction measurements demonstrated high crystalline quality homoepitaxial growth of these thin films. Atomic resolution STEM images of the as-grown β-Ga2O3 thin films on (010) and (001) substrates show high quality material without extended defects or dislocations. The charge carrier transport properties of the as-grown Si-doped β-Ga2O3 thin films were characterized by the temperature dependent Hall measurement using van der Pauw patterns. The room temperature carrier concentrations achieved for the (010) and (001) homoepitaxial thin films were ∼1.2 × 1018 cm−3 and ∼9.5 × 1017 cm−3 with mobilities of ∼72 cm2/V s and ∼42 cm2/V s, respectively.