Showing papers on "Van der Pauw method published in 2005"
TL;DR: In this paper, a spray pyrolysis technique was used to prepare films of undoped, fluorine-and antimony-doped tin oxide on glass at 400°C.
220 citations
TL;DR: In this paper, thin films of tin sulphide (SnS) have been used as an absorber for photovoltaic devices, and the properties of these films have been studied using EDAX, XRD, SEM, AFM, van der Pauw method and spectrophotometry.
Abstract: Thin films of tin sulphide $(Sn_xS_y)$ have been deposited on antimony-doped tin oxide-coated glass substrates using spray pyrolysis. The depositions were made using 0.1 M equimolar solutions of tin chloride and thiourea at different substrate temperatures varied in the range $100-450^0C$. The physical properties of the films were studied using EDAX, XRD, SEM, AFM, van der Pauw method and spectrophotometry. The obtained results were discussed in the view of testing the suitability of SnS films as an absorber for the fabrication of photovoltaic devices. The films formed for temperatures of $300-375^0C$ were nearly stoichiometric (Sn/S = 1.03), single phase (SnS) and showed a strong (1 1 1) preferred orientation with an average grain size of 0.37 $\mu$m. These single-phase films exhibited p-type conductivity with an average electrical resistivity of $30\Omega$cm and a net carrier concentration of $2 \times 10^1^5 cm^-^3$. These layers had a direct energy band gap of $\sim1.32eV$ with an absorption coefficient of $\sim10^5 cm^-^2$ above the fundamental absorption edge. The films deposited at temperatures $ 375^0C$ deviated from stoichiometry and additional phases were found to be present.
92 citations
TL;DR: In this article, the structural properties of ZnSe thin films have been investigated by XRD X-ray diffraction techniques and the lattice parameters, grain size, microstrain and dislocation densities were calculated and correlated with the substrate temperature.
Abstract: ZnSe thin films have been deposited on high cleaned glass substrate by spray
pyrolysis technique within the glass substrate temperature range (400 ○C
to 450 ○C). The structural properties of ZnSe thin films have been
investigated by (XRD) X-ray diffraction techniques. The X-ray diffraction
spectra showed that ZnSe thin films are polycrystalline and have a cubic
(zinc blende) structure. The most preferential orientation is along the
(111) direction for all spray deposited ZnSe films together with
orientations in the (220) and (311) planes also being abundant. The film
thickness was determined by an interferometric method. The lattice
parameter, grain size, microstrain and dislocation densities were calculated
and correlated with the substrate temperature (TS). The optical
properties of ZnSe thin films have been investigated by UV/VIS spectrometer
and the direct band gap values were found to be in the region of 2.65 eV to
2.70 eV. The electrical properties of ZnSe thin films have been investigated
using the Van der Pauw method and the high quality ZnSe thin films were
observed to develop at 430 ○C with a resistivity of 56,4×105 ohm cm, a conductivity of 1.77×10-7 (Ω cm)-1 and a hall
mobility of 0.53 cm2/Vsec.
72 citations
TL;DR: In this article, structural transformation and transformation kinetics of SbxSe100−x films (60⩽x墳70) were studied to investigate the feasibility of applying SbSe 100−x alloys in phase change nonvolatile memories.
Abstract: The structural transformation and transformation kinetics of SbxSe100−x films (60⩽x⩽70) were studied to investigate the feasibility of applying SbxSe100−x alloys in phase change nonvolatile memories. Temperature-dependent van der Pauw measurements, x-ray diffraction, x-ray reflectometry, and a static tester were used to determine the structure and transformation kinetics of the SbxSe100−x films. The sheet resistance difference between the amorphous and crystalline states was higher than 104Ω∕◻. The crystalline structure of the metastable phase of SbxSe100−x alloys, which plays a major role in fast crystallization, is similar to that of Sb2Te (rhombohedral structure). The transition temperature, sheet resistance, and activation energy for transformation decrease as the amount of Sb increases in the SbxSe100−x film. The density and thickness variation of the Sb65Se35 thin film were 5.9% and 5.4%, respectively. Applying the Kissinger method, the activation energies for crystallization were in the range from ...
56 citations
TL;DR: The van der Pauw technique is commonly used for electrical transport measurements on solid materials and is suited to thin, arbitrarily shaped samples, with the contacts placed anywhere on the periphery as mentioned in this paper.
Abstract: The van der Pauw technique is commonly used for electrical transport measurements on solid materials and is suited to thin, arbitrarily shaped samples, with the contacts placed anywhere on the periphery. Previous investigations have determined the effects of sample shape, contact size, and contact placement on the accuracy of this technique. Sample inhomogeneity effects have also been investigated. The effects of the sample thickness appear not to have been previously studied and are investigated here in order to establish precisely what is meant by a thin sample. The deterioration in the accuracy of the technique is followed as the sample thickness is increased. The results indicate that the van der Pauw technique may be used for samples where the thickness is comparable to the surface dimensions. The investigation also shows that the technique is valid for arbitrarily thick samples provided that low resistance electrodes are placed across the entire edge, perpendicular to the surface, in order to mainta...
55 citations
TL;DR: In this paper, structural electrical and optical properties of AgInS2 (AIS) thin films grown by the single-source thermal evaporation method were studied and the X-ray diffraction spectra indicated that the AIS single phase was successful grown by annealing above 400°C in air.
45 citations
04 Apr 2005
TL;DR: In this article, the fabrication of an InSb Hall sensor arrays to simultaneously detect multiple superparamagnetic microbeads for biomedical applications is described, where the authors showed that real-time simultaneous detection of multiple super-paramagnetic beads using the In Sb-Hall sensor array system is possible.
Abstract: In this report the fabrication of an InSb Hall sensor arrays to simultaneously detect multiple superparamagnetic microbeads for biomedical applications is described. One-dimensional InSb Hall sensor arrays with 8 micro-Hall devices were fabricated using photolithography and wet chemical etching. The electrical characteristics and noise spectrum of the micro-Hall sensors were determined by van der Pauw Hall measurements and fast Fourier transform (FFT) spectrum analysis respectively. Results show that the offset voltage of all 8 Hall sensors was small at /spl sim/0.1 mV under a drive current (I/sub H/) of 100 /spl mu/A. The minimum detectable magnetic field is found to be 0.10 mG/(Hz)/sup 1/2/ at I/sub H/ = 1 mA. Calculations showed that the magnetic field from a single ferromagnetic particle with a radius of 50 nm at a distance of 200 nm from the sensor is about 4.4 G. Therefore, the sensitivity of the Hall array micro-Hall sensors is sufficient for detection of magnetic microbeads. In conclusion, the paper showed that real time simultaneous detection of multiple superparamagnetic beads using the InSb-Hall sensor array system is possible. These results suggest that possibility of using two dimensional Hall sensor array biochips for biomedical applications.
33 citations
TL;DR: In this paper, the physical properties of the ternary single-phase Zr1−xAlxN compounds as a function of x over the range 0≤x≤0.43 were investigated.
29 citations
TL;DR: In this article, the optical and electrical properties of NbzSiyNx thin films deposited by dc reactive magnetron sputtering have been investigated as a function of the Si content (CSi).
Abstract: The optical and electrical properties of NbzSiyNx thin films deposited by dc reactive magnetron sputtering have been investigated as a function of the Si content (CSi). Optical properties were studied by both specular reflectivity and spectroscopic ellipsometry. Electrical resistivity was measured by the van der Pauw method at room temperature and as a function of the temperature down to 10K. Both the optical and electrical properties of NbzSiyNx films are closely related with the chemical composition and microstructure evolution caused by Si addition. For CSi up to 4at.% the Si atoms are soluble in the lattice of the NbN crystallites. In this compositional regime, the optical and electrical properties show little dependence on the Si content. Between 4 and 7at.% the surplus of Si atoms segregates at the grain boundaries, builds an insulating SiNx layer, and originates important modifications in the optical and electrical properties of these films. Further increase of CSi leads to the formation of nanocom...
28 citations
TL;DR: In this article, the authors reported electrical and optical properties of phosphate glasses containing Fe and Mn ions, one of which (Mn) does not contribute directly to conductivity, and the transport mechanism has been identified to be hopping of small polarons between Fe 2+ and Fe 3+ sites.
Abstract: The first article of this series reported electrical properties of phosphate glasses containing V and Fe ions, both of which contributed to conductivity. A mixed transition-ion effect was detected in such glasses which had several characteristics similar to the mixed alkali effect, observed in glasses containing two alkali ions. This article reports electrical and optical properties of phosphate glasses containing Fe and Mn ions, one of which (Mn) does not contribute directly to conductivity. DC resistivity by the Van der Pauw four-probe method and optical absorption (UV–VIS–IR) measurements have been performed on x P 2 O 5 − (100 − x ) (Fe 2 O 3 + MnO) (PFM) glasses. The transport mechanism has been identified to be hopping of small polarons between Fe 2+ and Fe 3+ sites. For 0.3 n Fe n Fe , the atomic fraction of Fe ions is given by (Fe/(P + Fe + Mn)), a marginal linear increase in resistivity has been observed with decreasing n Fe . However, when n Fe is reduced below ∼0.3, the resistivity increases exponentially with decreasing n Fe , which is similar to ‘metal–insulator transition’ (MIT), observed in many crystalline systems. The resistivity transition in these glasses has been explained by a (small) polaron to (small) bipolaron transition (PBT) in the composition range 0 ⩽ n Fe ⩽ 0.3. The occurrence of PBT is confirmed by the shifting of the polaronic optical absorption band to higher energies with increasing small bipolaron concentration.
22 citations
TL;DR: In this article, an apparatus capable of measuring the dc resistance versus temperature of a 49-member library prepared by thin-film deposition techniques was designed and tested, and the library is deposited by dc magnetron sputtering onto 10.16 cm×10.16cm alumina substrates on which are placed aluminum masks consisting of 8mm diam holes cut on a 7×7 grid, the center-tocenter spacing being 10.15mm.
Abstract: An apparatus, capable of measuring the dc resistance versus temperature of a 49-member library prepared by thin-film deposition techniques was designed and tested. The library is deposited by dc magnetron sputtering onto 10.16cm×10.16cm alumina substrates on which are placed aluminum masks consisting of 8mm diam holes cut on a 7×7 grid, the center-to-center spacing being 10.15mm. Electrical contact to the library is made in a standard van der Pauw geometry using 196 spring-loaded, gold-coated pins, four pins for each member of the library. The temperature is controlled using a helium refrigerator in combination with a liquid-nitrogen radiation shield that greatly reduces radiative heating of the sample stage. With the radiation shield, the cold finger is able to sustain a minimum temperature of 7K and the sample stage a minimum temperature of 27K. The temperature (27–291K) dependent dc resistivity of a thin-film silver library of varying thickness (48–639nm) is presented to highlight the capabilities of t...
TL;DR: In this paper, the van der Pauw method was used to study the magnetic properties and temperature dependence of electrical transport properties of rare-earth-metal Dy-doped GaN thin film with a superconducting quantum interference device magnetometer.
Abstract: Magnetic properties and temperature dependence of electrical transport properties of rare-earth-metal Dy-doped GaN thin film are experimentally studied with a superconducting quantum interference device magnetometer and van der Pauw method. It was found that this thin nitride film has both semiconductor properties and ferromagnetism from 10 K to room temperature. The dopant-band (conducting band due to doping) electron conduction dominates the transport properties of this film at low temperatures. These results indicate that Dy-doped GaN is an n-type ferromagnetic semiconductor at room temperature.
TL;DR: In this paper, single crystals of the lamellar compound, ZrSe3, were grown by chemical vapour transport technique using iodine as a transporting agent, and the grown crystals were characterized with the help of energy dispersive analysis by X-ray, which gave confirmation about the stoichiometry.
Abstract: Single crystals of the lamellar compound, ZrSe3, were grown by chemical vapour transport technique using iodine as a transporting agent. The grown crystals were characterized with the help of energy dispersive analysis by X-ray (EDAX), which gave confirmation about the stoichiometry. The optical band gap measurement of as grown crystals was carried out with the help of optical absorption spectra in the range 700–1450 nm. The indirect as well as direct band gap of ZrSe3 were found to be 1.1 eV and 1.47 eV, respectively. The resistivity of the as grown crystals was measured using van der Pauw method. The Hall parameters of the grown crystals were determined at room temperature from Hall effect measurements. Electrical resistivity measurements were performed on this crystal in the temperature range 303–423 K. The crystals were found to exhibit semiconducting nature in this range. The activation energy and anisotropy measurements were carried out for this crystal. Pressure dependence of electrical resistance was studied using Bridgman opposed anvils set up up to 8 GPa. The semiconducting nature of ZrSe3 single crystal was inferred from the graph of resistance vs pressure. The results obtained are discussed in detail.
TL;DR: In this paper, a thin film of molybdenum monoxide was deposited by metallorganic chemical vapour deposition and characterized using Rutherdford backscattering spectroscopy, Fourier transformed infrared and UV-Visible spectroscopies, X-ray diffraction, van der Pauw conductivity measurement and impedance spectrograms.
TL;DR: In this article, it was shown that both the SiC regions as well as the diamond matrix exhibit n-type conductivity and that the electron transport occurs across the low-resistivity SiC nanograins.
Abstract: Epitaxial SiC nanocrystals are fabricated by high-fluence Si implantation into natural diamond at elevated temperatures between 760 and 1100 °C. Fluences under investigation range from 4.5 to 6.2×1017Sicm−2. This implantation scheme yields a buried layer rich of epitaxially aligned SiC nanocrystals within slightly damaged diamond. The generation of a small fraction of graphitic sp2 bonds of up to 15% in the diamond host matrix cannot be avoided. Unintentional coimplantation with nitrogen results in a very high doping level of more than 1021cm−3. Resistivity and Hall measurements in van der Pauw geometry reveal a high, thermally stable n-type conductivity with electron concentrations exceeding 1020cm−3 and mobilities higher than 2cm2∕Vs. It is supposed that both the SiC regions as well as the diamond matrix exhibit n-type conductivity and that the electron transport occurs across the low-resistivity SiC nanograins. In the SiC nanocrystals the electrons originate from nitrogen donors whereas in diamond defe...
TL;DR: In this article, the authors presented a simple sequence for efficient external purification techniques, which consists of using thin nanoporous p-type silicon on both sides of the silicon substrates with randomly hemispherical voids.
Abstract: In this work, porous silicon damage (PSD) is presented as a simple sequence for efficient external purification techniques. The method consists of using thin nanoporous p-type silicon on both sides of the silicon substrates with randomly hemispherical voids. Then, two main sample types are processed. In the first type, thin aluminium layers (≥1 μm) are thermally evaporated followed by photo-thermal annealing treatments in N2 atmosphere at one of several temperatures ranging between 600 and 800 °C. In the second type, phosphorus is continually diffused in N2/O2 ambient in a solid phase from POCl3 solution during heating at one of several temperatures ranging between 750 and 1000 °C for 1 h. Hall Effect and Van Der Pauw methods prove the existence of an optimum temperature in the case of phosphorus gettering at 900 °C yielding a Hall mobility of about 982 cm2 V−1 s−1. However, in the case of aluminium gettering, there is no gettering limit in the as mentioned temperature range. Metal/Si Schottky diodes are elaborated to clarify these improvements. In this study, we demonstrate that enhanced metal solubility model cannot explain the gettering effect. The solid solubility of aluminium is higher than that of P atoms in silicon; however, the device yield confirms the effectiveness of phosphorus as compared to aluminium.
TL;DR: In this article, the diffusion of dopants at high doping concentrations (∼1020 cm−3) of GaSb, GaInAsSb and InAs sb grown in a molecular beam epitaxy system and doped with silicon, beryllium, and tellurium were investigated.
Abstract: Diffusion of dopants at high doping concentrations (∼1020cm−3) of GaSb, GaInAsSb, and InAsSb grown in a molecular beam epitaxy system and doped with silicon, beryllium, and tellurium were investigated. The electrically active doping concentration for each material was determined by van der Pauw measurements, while the doping profiles were measured by secondary-ion-mass spectroscopy. The samples were annealed to analyze the diffusion behavior. Two different growth techniques to achieve high doping levels were compared: δ dopings and deposition with reduced growth rate. The diffusion of Be in InAsSb:Be could not be prevented, neither by a low growth rate nor by intermediate GaSb spacers. A strong diffusion of Be and Te was found for δ-doped samples in InAsSb, whereas in slowly grown material the diffusion can be limited for Te as dopant.
TL;DR: In this paper, the authors studied the optical and electrical properties of Tb films as a function of hydrogen concentration and obtained the complex refractive index of the Tb film's complex dielectric function, e1 and e2.
Abstract: The absorption of hydrogen in the rare earth metals produces interesting changes in their optical and electrical properties. In this work we study these properties on Tb films, 50 nm thick, as a function of hydrogen concentration. The Tb films are covered with a 15 nm thick Pd overcoat which allows hydrogenation while protecting the highly reactive Tb film from contamination. Electrical resistivity is measured using the van der Pauw method, the transmission spectra are measured in the visible region and the concentration using a quartz crystal microbalance. The maximum concentration reached was 2.95 H/Tb at a hydrogen pressure of 450 Torr. From the measured transmission spectra, using a Spectral Projected Gradient Method, we obtain the Tb film's complex refractive index. From this we calculate the real and imaginary parts of the dielectric function, e1 and e2, and follow their evolution as a function of hydrogen concentration. e1 changes from negative values, characteristic of metals, to positive values characteristic of semiconductors and dielectrics. e2 decreases indicating a significant decrease in light absorption. These results are similar to those observed on Dy, Gd, La and Y films. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
TL;DR: In this paper, the electrical and optical properties of H+ and Au+-irradiated InGaAs layers were studied using Hall-effect, van der Pauw, and relaxation-time measurements.
Abstract: The electrical and optical properties of H+- and Au+-irradiated InGaAs layers were studied using Hall-effect, van der Pauw, and relaxation-time measurements. Comparing the different results allows us to obtain information on the nature of the defects created by these two irradiations. Proton irradiation introduces donor-acceptor paired defects. Gold-ion irradiation creates neutral defect clusters and ionized point defects. The carrier mobilities in all of the irradiated materials are degraded, decreasing with increasing irradiation dose. A scattering model taking into account the paired defects is developed and the mobility evolution calculated from this model agrees with the experimental data of both annealed and unannealed samples. The photocurrent spectra reveal a metallic conduction in the band gap in the case of light-ion irradiation, while such type of conduction does not appear for heavy-ion irradiation. This metallic conduction is a consequence of band tailing induced by shallow defects and vanish...
TL;DR: In this paper, structural and electrical properties of AgInS2 (AIS) thin films grown by single-source thermal evaporation method were studied, and X-ray diffraction spectra indicated that the AIS single phase was successfully grown by annealing above 400∘C in air.
Abstract: Structural and electrical properties of AgInS2 (AIS) thin films grown by single-source thermal evaporation method were studied The X-ray diffraction spectra indicated that the AIS single phase was successfully grown by annealing above 400∘C in air The grain size of the AIS crystals was above 25 μm from the surface photograph Furthermore, the AIS grain sizes became large with increasing the annealing temperatures All the samples indicated n-type conduction by the Van der Pauw technique The carrier concentrations and the resistivities of the AIS films at room temperature were in the range of 1019–1022 cm−3 and 10−1–10−3 Ωcm, respectively Therefore the mobilities increased from 06 to 60 cm2/Vs with increasing the grain sizes
19 Jun 2005
TL;DR: In this paper, the electrical resistivity of a thermoelectric composite was investigated in an in-plane test geometry (van der Pauw configuration) and in a perpendicular-to-the-plane (cross-plane) test geometry.
Abstract: Advanced bulk thermoelectric materials have been developed by fabricating composites of uniformly distributed thermoelectric nanoparticles within a high surface area semiconductor matrix. In this composite structure, constituents of the thermoelectric materials' figure of merit can be decoupled and controlled independently, and consequently, one can achieve a high thermoelectric figure of merit. The produced composites exhibited extremely low thermal conductivity and relatively high electrical conductivity. However, the Seebeck coefficient was relatively low, probably due to poor quality of the thermoelectric particles. In an in-plane test geometry (van der Pauw configuration), the electrical resistivity of the composite sample decreased continuously as temperature increased, a typical semiconductor behavior. In the perpendicular-to-the-plane (cross-plane) test geometry, electrical resistance of the sample increased continuously with increasing temperature, probably a semi-metallic behavior. This anisotropy in the electrical resistance was reproducible. We also observed relatively strong high frequency AC-signals in the in-plane test geometry samples.
TL;DR: In this article, powder and crystal structures were examined by X-ray diffraction and the transport and magnetic characteristics were measured, where powders resulted to be single-phase and the relevant composition was assumed to be equal to the nominal one.
Abstract: Vn-xTixO2n-1 Magneli phases have been synthesized under vacuum in powder form (n = 4, 0 ≤ x ≤ 0.4) and crystals (n = 4 and 5, x = 0.5 and 1.4, respectively), grown by chemical vapour transport in closed ampoules. TeCl4 and NH4Cl were used as transporting agents. Needle-shaped crystals as long as 200-300 micrometers or 2-3 mm were obtained when in presence of NH4Cl or TeCl4, respectively. The powder and crystal structures were examined by X-ray diffraction and the transport and magnetic characteristics were measured.. The powders resulted to be single-phase and the relevant composition was assumed to be equal to the nominal one. The overall stoichiometry of compounds, n, was determined from single crystal X-ray diffraction data. The Ti content, x, was deduced from the elementary cell volume, by applying the Vegard law. Crystals were mainly untwinned and of good quality. The elementary cell of both, powders and crystals, was triclinic (P-1) and did not change with doping. DC electrical resistivity of the crystals was measured in a four-points (van der Pauw) configuration. DC magnetic susceptibility of the powders was measured in a SQUID magnetometer. The Ti doping was found to progressively smooth and finally to suppress the magnetic transitions occurring in the V4O7. The metal-insulator transitions observed in V4O7 and V5O9, at around 235 and 125 K respectively, were not observed in the doped crystals, thus indicating some significant change of the electronic structure of the V oxides. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
TL;DR: In this paper, high-dose ion implantation of phosphorus into 4H-SiC (0001) has been investigated with three different ion fluxes ranging from 1.0 to 4.0 x 10(12) P(+)cm(-2.)s(-1) and keeping the implantation dose constant at 2.0.
Abstract: High-dose ion implantation of phosphorus into 4H-SiC (0001) has been investigated with three different ion fluxes ranging from 1.0 to 4.0 x 10(12) P(+)cm(-2.)s(-1) and keeping the implantation dose constant at 2.0 x 10(15) P(+)cm(-2). The implantations are performed at room temperature and subsequently annealed at 1500 degrees C. Photoluminescence and Raman scattering are employed to investigate the implantation-induced damages and the residual defects after annealing. The electrical properties of the implanted layer are evaluated by Hall effect measurements on the sample with a van der Pauw configuration. Based on these results, it is revealed that the damages and defects in implanted layers can be greatly reduced by decreasing the ion flux. Considering room temperature implantation and a relatively low annealing temperature of 1500 degrees C, a reasonably low sheet resistance of 106 Omega/square is obtained at ion flux of 1.0 x 10(12) P(+)cm(-2.)s(-1) with a donor concentration of 4.4 x 10(19)cm(-3).
TL;DR: In this article, thin films of LixMoyOz have been deposited on a glass substrate in a one-step chemical vapour deposition using a single source solid precursor.
Abstract: Thin films of LixMoyOz have been deposited on glass substrate in a one step chemical vapour deposition using a single source solid precursor. The films were characterized using Rutherford Backscattering Spectroscopy (RBS), X-Ray Diffractometry, Scanning Electron Microscopy (SEM), Impedance Spectroscopy (IS), van der Pauw conductivity measurement and Ultraviolet-Visible Spectroscopy. Results of the characterization showed that the films are dendritic, polycrystalline and semiconducting with an optical transition energy of 3.0 eV. IS characterization gave a semicircle in the complex impedance plot. The conductivity vs. temperature plot showed a transition at 450 °C and also a hysteresis. Analysis showed the film to be mixture of phases.
TL;DR: In this paper, the authors calculated the lithium diffusion coefficient and dc conductivity for Li x (Ni 0. 8 Co 0. 2 )O 2 composite by Galvanostatic Intermittent Titration Techniques (GITT) and Van der Pauw method.
Abstract: Several authors have proposed that lithium diffusivity is the restrictive step in the insertion and extraction lithium processes in Li 1 - x [Ni ( y - x ) Ni x ]Co 1 - y O 2 cathodic oxides. In this article we calculated the lithium diffusion coefficient and dc conductivity for Li x (Ni 0 . 8 Co 0 . 2 )O 2 and Li x (Ni 0 . 8 Co 0 . 2 )O 2 /PANI composite by Galvanostatic Intermittent Titration Techniques (GITT) and Van der Pauw method, respectively. These materials were previously synthesized by novel chemical ways. Transport measurements indicated that the electronic and ionic transports are greater for composite than for the oxide. This effect was particularly evidenced by the better reversibility of Li-insertion in charge-discharge cycles in a lithium battery prototype for composite.
TL;DR: In this paper, the homogeneity of electrical properties in the case of co-implanted nitrogen and phosphorus ions in 4H-SiC semi-insulating wafers was investigated.
Abstract: We report a full wafer size investigation of the homogeneity of electrical properties in the case of co-implanted nitrogen and phosphorus ions in 4H-SiC semi-insulating wafers. To match standard industrial requirements, implantation was done at room temperature. To achieve a detailed electrical knowledge, we worked on a 35 mm wafer on which 77 different reticules have been processed. Every reticule includes one Hall cross, one Van der Pauw test structure and different TLM patterns. Hall measurements have been made on all 77 different reticules, using an Accent HL5500 Hall System® from BioRad fitted with an home-made support to collect data from room temperature down to about 150 K. At room temperature, we find that the sheet carrier concentration is only 1/4 of the total implanted dose while the average mobility is 80.6 cm2/Vs. The standard deviation is, typically, 1.5 cm2/Vs.
TL;DR: In this article, the effect of tungsten sputtering on the transport properties of these shallow channels was investigated and it was shown that substrate damage can be minimized by using low sputtering currents, a large source to substrate distance, and a high sputtering pressure.
Abstract: This article investigates sputter-induced damage caused by direct current magnetron sputter coating of tungsten on GaAs based high electron mobility transistor layer structures with channels buried less than 20nm from the surface. Van der Pauw structures were used to study the effect of tungsten sputtering on the transport properties of these shallow channels. Using this approach we established that substrate damage can be minimized by using low sputtering currents, a large source to substrate distance, and a high sputtering pressure. Unfortunately such sputtering conditions do not produce the best quality dense films necessary for device fabrication and it was necessary to establish conditions which were a compromise of film quality and substrate damage. Postsputter annealing was found to significantly reduce the damage and a loss of 10% in semiconductor conductivity was obtained for good quality tungsten films.
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TL;DR: In this paper, a simple electronic circuit using four common and inexpensive analog multiplexer/demultiplexer chips was described using analog switches used to select eight different wiring configurations to a van der Pauw sample.
Abstract: A simple electronic circuit is described using four common and very inexpensive analog multiplexer/demultiplexer chips. These analog switches are used to select eight different wiring configurations to a van der Pauw sample. Several interfacing schemes to a PC are suggested. The van der Pauw resistivity and Hall voltage expressions are also summarized.
01 Jan 2005
TL;DR: In this paper, an automatic measuring system (AMS) is proposed to obtain the carrier concentration profile n(x), and mobility profile µ(x) from the sheet resistance and sheet Hall mobility by van der Pauw measurements.
Abstract: This article deals with the design, construction and a control program of an automatic measuring system (AMS). The AMS allows to obtain the carrier concentration profile n(x) and mobility profile µ(x) from the sheet resistance and sheet Hall mobility by van der Pauw measurements, while gradually removing layers of the semiconductor by anodization/etch procedures. AMS can also be used for sheet resistance measurements by the four-point-probe method and for calculating the specific resistance. Further, the software of the AMS contains graphical subroutines for conversion of resistivity to concentration and mobility. The experimental n(x) profile has been compared with that calculated by program SUPREM. K e y w o r d s: Hall system, van der Pauw, Si, four point probe, SUPREM
TL;DR: In this article, a single source vacuum evaporation process has been employed to prepare thin films of Cu 2 S n S 3, and electrical Hall measurements using Van der Pauw technique have revealed that film resistivity was a strong function of the substrate temperature for film deposition.
Abstract: A single source vacuum evaporation process has been employed to prepare thin films of Cu 2 S n S 3 . Electrical Hall measurements using Van der Pauw technique have revealed that film resistivity was a strong function of the substrate temperature for film deposition. The activation energy for the resistivity was 0.268 eV for films deposited at 300 K, 0.162 eV for films deposited at 423 K and 0.059 eV for films deposited at 573 K. The Hall mobility was observed to decrease with an increase in temperature due to grain boundary scattering. Room temperature mobility was 110 cm 2 V -1 s -1 , reducing to 28 cm 2 V -1 s -1 at 593 K. The barrier height within the grain was determined to be 0.051 eV. Key words: Thin film, transport properties, vacuum evaporation, activation energy, Hall mobility Nig. J. of Pure & Appl. Physics Vol.3 2004: 75-78