Hall Effect Results Research Articles

Structure, Optical, Temperature Dependent Electrical Properties of P-Type Conduction in N–Al Codoped Zn<sub>1-X</sub>Mg<sub>X</sub>O Films by Ultrasonic Spray Pyrolysis

Four series of thin films have been deposited as the precursory sources of Zn(CH3COO)2, Mg(CH3COO)2, NH4CH3COO and AlCl3 aqueous solutions using ultrasonic spray pyrolysis (USP) method. The crystalline structure, morphology images, electrical, optical properties of the films are characterized by x-ray diffraction (XRD), field emission-scan electron image (FE-SEM), Hall-effect measurement and photoluminescence (PL). From the XRD patterns and SEM images, we can see that all the films present good crystallinity and surface uniformity. Hall-effect measurement results indicate that ZnO is n-type, while N-Al codoped ZnO and N-Al codoped Zn1-xMgxO exhibit p-type conduction. Temperature dependent of electrical measurement is carried out from 300K to 500K, then the conductive mechanism and carriers scattering are analysed. Furthermore, the photoluminescence peak of Zn1-xMgxO is tuned into shorten wavelength than pure ZnO (λ＝379－352＝27nm), and also the same phenomenon of the p-type Zn1-xMgxO film exhibits blue-shifted behavior from 378nm to 356nm compared with p-type ZnO film (λ＝378－356＝21nm). In other word, the p-type Zn1-xMgxO film shifts to a shorter wavelength of 356 nm while maintaining excellent electrical performances.

Different effects of Ni and Co substitution on the transport properties of BaFe2As2

We report resistivity and Hall effect results on Ba(Fe1-xNix)2As2 and compare them with those in Ba(Fe1-xCox)2As2. The Hall number RH is negative for all x values from 0.01 to 0.14, which indicates that electron carriers dominate the transport both in the magnetic and paramagnetic regime. We analyse the data in the framework of a two-band model. Without any assumption on the number of carriers, we show that the electron resistivity can be estimated with good accuracy in the low temperature paramagnetic range. Although the phase diagrams of the two families are very similar with respect to the extra electrons added in the system, we find that the transport properties differ in several aspects. First, we evidence that the contribution of holes to the transport is more important for Ni doping than for Co doping. Secondly, Ni behaves as a stronger scatterer for the electrons, as the increase of the residual electron resistivity rho/x is about four times larger for Ni than for Co in the most doped samples.

The structural and electrical studies on the Boron-doped SnO 2 films deposited by spray pyrolysis

The boron-doped SnO 2 (BTO) films were prepared by spray pyrolysis. The XRD results shows the preferred orientation of the BTO films changes from plane (110) to (101) as the increasing of boron concentration in SnO 2, which further leads to the variation of grains shape on the surfaces. The FTIR and Hall-Effect results indicate the solution process: the boron ions prefer to occupy the interstitial site in SnO 2 lattice, which play the role of donor of free electrons; while beyond a certain boron concentration, boron ions start to replace the tin ions of lattice, which has a negative effect on carrier concentration. The scattering mechanism of BTO is also discussed in the paper based on the grain size and meal free path.

Structural, electrical and optical properties of p-type transparent conducting SnO2:Al film derived from thermal diffusion of Al/SnO2/Al multilayer thin films

Highly transparent, p-type conducting SnO2:Al films derived from thermal diffusion of a sandwich structure Al/SnO2/Al multilayer thin films deposited on quartz substrate have been prepared by direct current and radio-frequency magnetron sputtering using Al and SnO2 targets. The deposited films were annealed at various temperatures for different durations. The effect of thermal diffusing temperature and time on the structural, electrical and optical performances of SnO2:Al films has been studied. X-ray diffraction results show that all p-type conducting films possessed polycrystalline SnO2 with tetragonal rutile structure. Hall-effect results indicate that 450°C for 4h were the optimum annealing parameters for p-type SnO2:Al films, resulting in a relatively high hole concentration of 7.2×1018cm−3 and a low resistivity of 0.81Ωcm. The transmission of the p-type SnO2:Al films was above 80%.

Effect of thermal annealing on the microstructural and electrical properties of Al-doped ZnO thin films grown on n-Si (1 0 0) substrates

Transmission electron microscopy (TEM) images for the Al-doped ZnO (AZO) films grown on n-Si (1 0 0) substrates and annealed for 10 min at 900 and 1000 °C showed that an amorphous phase region appeared in the grain boundaries of the AZO thin films by tilting the TEM specimen and that the amorphous phase did not show the constrast variation with change in the zone axis of the specimen. High-resolution TEM images revealed that the single grains existing around the amorphous region contained a higher dislocation density in comparison with the polycrystalline region. Hall effect results showed that the mobility of the annealed AZO thin films was smaller than that of the as-grown AZO thin films and that the resistivity of the annealed AZO thin films was larger than that of the as-grown AZO thin films.

Electrical and Raman Scattering Studies of ZnO:P and ZnO:Sb Thin Films

A study on the structure, electrical and optical properties of ZnO thin films produced by r.f. magnetron sputtering and implanted either with phosphorous (P) or antimony (Sb) is reported in this work. Raman spectroscopy, X-ray diffraction, optical transmittance and Hall effect measurements have been employed to characterize the samples. X-ray diffraction and Raman scattering patterns confirm that, after a 500 degrees C annealing, the doped films keep a polycrystalline nature with (002) preferred orientation. These films are very transparent and Hall effect results show that all have p-type conduction, despite doping ion and dose. The electric resistivity reaches values of 0.012 (omega cm) and 0.042 (omega cm) for the P and Sb-doped samples, respectively.

Frequency doubling and memory effects in the spin Hall effect

We predict that when an alternating voltage is applied to a semiconducting system with inhomogeneous electron density in the direction perpendicular to main current flow, the spin Hall effect results in a transverse voltage containing a double-frequency component. We also demonstrate that there is a phase shift between applied and transverse-voltage oscillations, related to the general memristive behavior of semiconductor spintronic systems. A different method to achieve frequency doubling based on the inverse spin Hall effect is also discussed.

Microwave shielding of fluorine-doped tin oxide film obtained by spray pyrolysis studied by electrical characterization

In this work, we report dc conductivity and Hall effect results for glasses coated with commercial In2O3:Sn and SnO2:F. Van der Pauw Hall effect and resistivity measurements were used to carry out the sheet resistance of the samples and to determine their carrier density, mobility, and conductivity from 10 to 325 K. We calculated the transmission from the dc measurements and compared it with the microwave response of a typical microwave oven door used as a barrier on a cavity resonator, at 2.8 GHz. By controlling the oxygen doping through the H2O amount in the solution, we were able to increase the mobility of SnO2:F sample and as a consequence obtained an improved microwave shielding power. We estimated that, for the best case, a coating 13.2 μm thick should suffice for a shielding power similar to that of a microwave oven door.

Hall effect in

Abstract We present Hall effect measurements of two-leg ladder Sr 14 - x Ca x Cu 24 O 41 ( 0 ⩽ x ⩽ 11.5 ). In these composite materials charge and spin ordering occur within chain and ladder subsystems. They have been investigated intensively during the last years because of their fascinating physical properties, especially after the discovery of superconductivity under pressure (for x > 10 ). They are the first superconducting copper oxides (superconductivity occurs under pressure for x > 10 ) without the CuO 2 planes, characteristic for high-temperature superconductors. The question of charge dynamics and hole distribution between the ladders and chains is still open. Our Hall effect results show typical semiconducting behavior for x 10 . The x = 11.5 compound shows metallic behavior and our Hall effect results match qualitatively the behavior found in high- T c cuprates. We have determined the effective number of carriers and its dependence on composition (x) and compared it to the number of holes in the ladders obtained by other experimental techniques at room temperature.

CALCULATE THE VALUES OF SOME PHYSICAL PROPERTIES OF Se0.3Te0.7 ALLOY PREPARED AT DIFFERENT SUBSTRATE TEMPERATURES

In this paper; Se0.3Te0.7 alloy was prepared by mixing Selenium and tellurium of high purity using vacuum evaporation technique, this alloy was prepared as thin films at different substrate temperature; (25, 50, 100, 150) C o . The annealing was done for some of the prepared films at 200 o C. The powder of the prepared alloy was tested by X-Ray diffraction; the result shows that the structure of the Se0.3Te0.7 alloy was polycrystalline. From Hall effect results; the films was found as p-type, the density of the charge carriers (N) was calculated at different substrate temperature, the concentration of charges carriers of the annealed films was decreased. The optical properties of Se0.3Te0.7 films were studied, the values of the optical energy gaps were calculated and it was 0.48 eV at room temperature, this value was increase at the increasing of the substrate temperature. The value of energy gap of the annealed film was calculated and it was 0.62 eV at room temperature. The refraction index was calculated at room temperature as a function of the wave length at 2100 nm; it found to be 4.2.

Spin Hall effect of excitons

Spin Hall effect for excitons in alkali halides and in ${\text{Cu}}_{2}\text{O}$ is investigated theoretically. In both systems, the spin Hall effect results from the Berry curvature in $k$ space, which becomes nonzero due to lifting of degeneracies of the exciton states by exchange coupling. The trajectory of the excitons can be directly seen as spatial dependence of the circularly polarized light emitted from the excitons. It enables us to observe the spin Hall effect directly in the real-space time.

Electrical, structural, photoluminescence and optical properties of p-type conducting, antimony-doped SnO 2 thin films

P-type transparent conducting antimony-doped tin oxide (ATO) films were successfully fabricated on quartz glass substrates by radio-frequency magnetron sputtering using a 20 mol.% Sb-doped SnO 2 ceramic target. The deposited films were annealed at different temperatures for different durations. Hall effect results indicated that 973 K was the optimum annealing temperature to get p-type ATO films with the highest hole concentration (5.83 × 10 19 cm –3). X-ray diffraction studies indicated that the preferred (1 0 1) orientation favored the formation of p-type conducting films. Photoluminescence spectra showed an intense UV luminescence peak near 362 nm resulting from the band-edge exciton transition observed for p-type ATO films. UV–visible transmission spectra showed that p-type ATO films had high transparence. In addition, p-type conductivity was also confirmed by the non-linear characteristics of a p-type ATO/n-type ATO structure; the diode structure has an optical transmission of ∼60–85% in the visible light range.

Possible anomalous Hall effect of Be/Si pair delta‐doped GaAs structures

AbstractBeryllium/Silicon pair delta‐doped GaAs structures grown by molecular‐beam epitaxy exhibit Hall resistance which has highly nonlinear dependence on the applied magnetic field. The dependence of the occurrence of the nonlinear Hall resistance on the sample structure is investigated. A significantly large increase in the non‐linearity and magnitude of the Hall resistance is observed from a sample structure whose buffer layer is grown under the low As flux and thick buffer layer condition. The non‐linearity of the Hall resistance is found to depend on a single parameter B /T, where B and T are the magnetic field and temperature, respectively. From another sample structure in which an AlGaAs barrier with a single Be delta‐doped layer is placed near the Be/Si pair delta‐doped layer, a similar nonlinear Hall resistance is observed. On the basis of these results, it is suggested that the anomalous Hall effect results from interplay between itinerant holes in the valence band and localized spins in the delta‐doped layer in these structures. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Field-Induced Fermi Surface Reconstruction and Adiabatic Continuity between Antiferromagnetism and the Hidden-Order State inURu2Si2

Shubnikov-de Haas oscillations reveal at high fields an abrupt reconstruction of the Fermi surface within the hidden-order (HO) phase of URu2Si2. Taken together with reported Hall effect results, this implies an increase in the effective carrier density and suggests that the field suppression of the HO state is ultimately related to destabilizing a gap in the spectrum of itinerant quasiparticles. While hydrostatic pressure favors antiferromagnetism in detriment to the HO state, it has a modest effect on the complex H-T phase diagram. Instead of phase separation between HO and antiferromagnetism our observations indicate adiabatic continuity between both orderings with field and pressure changing their relative weight.

Surface electronic properties on boron doped (111) CVD homoepitaxial diamond films after oxidation treatments

Surface electronic properties on oxidized boron (B) doped (111) homoepitaxial diamond films are investigated by Hall effect measurements and Schottky junction characterizations. Surface electronic properties on (111) diamond strongly depend on annealing treatments after wet-chemical oxidation, whereas for those on (001) diamond no change due to annealing can be detected. Hall effect results show that a p-type surface conductive layer (SCL) exists on (111) diamond surface in air after wet-chemical oxidation followed by annealing in Ar atmosphere (WO–AN) above 300 °C, but does not if only wet-chemical oxidation or air-oxidation is applied. This SCL disappears at annealing temperature above 350 °C in air. Schottky junction characteristics suggest that the Fermi level is unpinned at the (111) surface after WO–AN. Surface electronic characteristics on (111) diamond after WO–AN are similar to those generated by hydrogen termination.

Evidence for a quantum phase transition in electron-dopedPr2−xCexCuO4−δfrom thermopower measurements

The evidence for a quantum phase transition under the superconducting dome in the high-${T}_{c}$ cuprates has been controversial. We report low-temperature normal state thermopower $(S)$ measurements in electron-doped ${\mathrm{Pr}}_{2\ensuremath{-}x}{\mathrm{Ce}}_{x}\mathrm{Cu}{\mathrm{O}}_{4\ensuremath{-}\ensuremath{\delta}}$ as a function of doping ($x$ from 0.11 to 0.19). We find that at $2\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ both $S$ and $S∕T$ increase dramatically from $x=0.11$ to 0.16 and then saturate in the overdoped region. This behavior has a remarkable similarity to previous Hall effect results in ${\mathrm{Pr}}_{2\ensuremath{-}x}{\mathrm{Ce}}_{x}\mathrm{Cu}{\mathrm{O}}_{4\ensuremath{-}\ensuremath{\delta}}$. Our results are further evidence for an antiferromagnetic to paramagnetic quantum phase transition in electron-doped cuprates near $x=0.16$.

THE HALL EFFECT AND MICROSTRUCTURES OF (Fe0.86Zr0.033Nb0.033B0.068Cu0.01)x(Al2O3)1-xGRANULAR FILMS

A series of ( Fe0.86Zr0.033Nb0.033B0.068Cu0.01)x( Al2O3)1-xgranular films of about 100 nm thick were deposited on the glass substrate using the magnetron sputtering technique. Hall resistivity was measured using a four-terminal method at room temperature in the field of 1.1 Tesla. As x increases, the Hall resistivity of the samples rises and reaches a maximum of 17.5 μΩ-cm at x = 0.43, which is about three orders of magnitude greater than those of pure magnetic metal samples, and for further increase of x, the Hall resistivity decreases. For as-deposited x = 0.43 sample, transmission electron microscopy (TEM) images shows the microstructural characteristics of granular films around percolation threshold. The temperature dependence of resistivity shows that the conduction behavior changes from insulator to metal with the increment of metal fraction, and for sample x = 0.43, the conduction behavior is located in the transition region from insulator to metal, near the percolation value, which is consistent with the above experimental results. It is suggested that the enhancement of Hall effect results from not only the magnetic metal fraction but also the microstructure characteristic of percolation system.

Preparation and properties of the trivalent-ion doped tungsten bronze LaxWO3

The production and characterization of lanthanum-doped tungsten oxide, LaxWO3, sintered samples are presented for 0.05⩽x⩽0.23. The x-ray diffraction results show that the cubic perovskite phase is stable for x in the range of 0.086–0.21. Outside of this range additional phases are present. Resistivity measurements made between 64 and 300K provide information on the electronic properties. Room temperature Hall effect results show that the trivalent La ions donate their valence electrons into the WO3 conduction band. The samples have been prepared for an investigation of the metal-insulator transition in this tungsten bronze system.

Hall effect and Raman analysis of residual damage and free electron concentration in Si-implanted GaAs: a quest for better doping efficiency

To tackle the problem of insufficient electrical activation of Si + dopant in GaAs, we have studied a series of heavily Si-implanted and thermally annealed GaAs samples (two different doses, each implanted at three different temperatures and with two implantation rates). A comparative analysis of electrical and optical measurements was done on the same set of samples and correlated with implantation parameters. By temperature dependent Hall-effect measurements carrier density and carrier mobility were determined over the 20–300 K range. The mobility data were analyzed taking into account different scattering mechanisms. The implantation-induced initial damage was determined by Rutherford backscattering, whereas the amount of residual damage present in the samples after thermal annealing was estimated by Raman spectroscopy. Additionally, scattering by LO phonon–plasmon coupled modes was used to study the properties of the free electron gas in the implanted layer, including its depth distribution. Free carrier concentrations deduced from the analysis of the plasmon modes agree with the Hall-effect results. Multi-energy implantation in combination with higher implant temperature is suggested as a way to increase doping efficiency by reducing high local concentrations and lessen the probability of compensating defects formation.

Influence of arsenic temperature on the structural and electrical characteristics of InAsSb layers grown on GaAs by hot wall epitaxy

Abstract We have studied the structural and electrical characteristics of InAsSb ternary layers grown on GaAs (0 0 1) substrates by hot wall epitaxy at arsenic (As) reservoir temperature in the range from 220 to 290 °C. The growth rate of the epilayer is found to decrease with increasing As temperature. This is attributed to the abundance of group V molecules to the growth surface, which suppresses the mass transport of indium (In) atoms. A dramatic change in the surface morphologies of the samples has been observed by scanning electron microscopy. X-ray diffraction studies indicate that the arsenic composition of the layer can be controlled by manipulating As temperature. Hall effect results of the samples show that the electron mobility of the layer decreases with increasing As temperature.