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.

Thermal oxidation of sputtered nickel nano-film as hole transport layer for high performance perovskite solar cells

Abstract: The effect of rapid oxidation temperature on the sputtered nickel (Ni) films to act as a hole transport layer (HTL) for perovskite solar cell (PSCs) was investigated. A nano-sputtered Ni film with a thickness about 100 nm was oxidized at a range of different oxidation temperatures between 350 and 650 °C to work as HTL in an inverted p–i–n configuration. DC Hall measurement in van der Pauw configuration and photoluminescence spectroscopy were used to measure the charge’s mobility and extraction of nickel oxide (NiO) films. The behaviour of the carrier concentration measurements of NiO layers at different oxidation temperatures showed that the Ni layer oxidized at 450 °C had the highest carrier concentration among the other samples. The performance measurements of the fabricated PSCs showed that the nickel oxide hole-transporting layer which has been oxidized at the optimum oxidation temperature of 450 °C has the highest power conversion efficiency (PCE) of 12.05%. Moreover, the characteristic parameters of the optimum cell such as the open-circuit voltage (VOC), short-circuit current density (JSC) and fill factor (FF) were 0.92 V, 19.80 mA/cm2 and 0.331, respectively.

Metamorphic high electron mobility Te-doped AlInSb/GaInSb heterostructures on InP (001)

Abstract: This work reports on the Te δ-doping of high electron mobility AlInSb/GaInSb heterostructures grown by molecular beam epitaxy on InP(001) substrates with a metamorphic approach. The combination of atomic force microscopy and van der Pauw measurements is used to investigate and explain the influence of the buffer layers on the electron mobility and sheet density in the heterostructure. Furthermore, a significant increase in the electron sheet density is reached when the δ-doping plane is incorporated in a thin AlSb layer introduced in the barrier. This improvement is explained by the lower dopant activation energy in the AlSb layer. AlInSb/GaInSb heterostructures with an electron mobility of 18 000 cm2/V s and sheet density of 2.2×1012 cm−2 at room temperature are demonstrated.

Effects of phosphorus doping via Mn3P2 on diamond growth along the (100) surfaces

Abstract: In this study, diamond crystals were synthesized via the temperature gradient method at 5.6 GPa and 1230–1245 °C by adding a Mn3P2 dopant and FeNi catalyst. Experimental results showed that Mn3P2 shifted the V-shaped growth region to the upper right by influencing the catalytic properties. The scanning electron microscopy (SEM) photographs of the diamonds synthesized at 1245 °C revealed that there were many dendritic structures in the (100) surfaces. The diamond crystal quality could be improved when the added Mn3P2 was less than 6 wt% at 1245 °C, but it would be seriously damaged when the diamond was heavily doped with Mn3P2. Pits and uneven layered structures appeared on the diamond surfaces when the additive was included at 12 wt% at 1245 °C. The Fourier transform infrared spectroscopy (FTIR) results revealed that the Mn3P2 additive increases the N content of the crystal and that N is present in the diamond crystal in the form of a “C” center. It is worth noting that phosphorus could be doped into diamond crystals by using the Mn3P2 additive and that the other impurities in diamonds were mostly C–N and C–O forms, as confirmed by X-ray photoelectron spectroscopy (XPS). The phosphorus in the sample crystals mainly formed C–P bonds with carbon, while a smaller amount of phosphorus formed P–O bonds with oxygen. The test results of the electrical properties as assessed by the van der Pauw method for the diamond crystals with Mn3P2 doped at 1245 °C revealed a resistivity of 0.516 × 106–9.729 × 106 Ω cm and a negative Hall coefficient, indicative of an n-type semiconductor.

Anomalous grain boundary and carrier transport in cat-CVD poly-Si films

Abstract: Polycrystalline silicon (poly-Si) films are obtained at temperatures less than 400°C by catalytic chemical vapor deposition (cat-CVD) method, often called `hot-wire CVD' method. Structural properties of the cat-CVD poly-Si films are studied by Raman spectroscopy and high resolution transmission electron microscopy, along with carrier transport properties measured by the Van der Pauw method. It is found that the cat-CVD poly-Si films have a microstructure which consists of columnar crystalline grains with tens of nanometers diameter and a few nm thick amorphous layers surrounding the columnar grains. It is also found that the Hall mobilities of some samples are several-tens cm 2 /V s and the barrier heights at the grain boundaries become the order of 0.01 eV or less. These good carrier transport properties appear dependent on the grain boundary structure of the cat-CVD poly-Si films.

Improved optical and electrical properties of sol–gel-derived boron-doped zinc oxide thin films

Abstract: Sol–gel spin-coating was used to grow zinc oxide (ZnO) thin films doped with 0–2.5 at.% B on quartz substrates. The structural, optical, and electrical properties of the thin films were investigated using field-emission scanning electron microscopy, X-ray diffraction (XRD), photoluminescence (PL), ultraviolet–visible spectroscopy, and van der Pauw Hall-effect measurements. All the thin films had deposited well onto the quartz substrates and exhibited granular morphology. The average crystallite size, lattice constants, residual stress, and lengths of the bonds in the crystal lattice of the thin films were calculated from the XRD data. The PL spectra showed near-band-edge (NBE) and deep-level emissions, and B doping varied the PL properties and increased the efficiency of the NBE emission. The optical transmittance spectra for the undoped ZnO and boron-doped zinc oxide (BZO) thin films show that the optical transmittance of the BZO thin films was significantly higher than that of the undoped ZnO thin films in the visible region of the spectra and that the absorption edge of the BZO thin films was blue-shifted. In addition, doping the ZnO thin films with B significantly varied the absorption coefficient, optical band gap, Urbach energy, refractive index, extinction coefficient, single-oscillator energy, dispersion energy, average oscillator strength, average oscillator wavelength, dielectric constant, and optical conductivity of the BZO thin films. The Hall-effect data suggested that B doping also improved the electrical properties such as the carrier concentration, mobility, and resistivity of the thin films.