Preparation and electrical properties of InSe

Abstract

Single crystals of Indium Selenide are prepared by vapour growth technique as it is difficult to prepare large single crystals by vertical Bridgman technique. The effect of stochiometric changes and doping have been studied. The electrical properties of n-type single crystals are discussed.     

Thermoelectric properties and structural instability of type-I clathrate Ba8Ga16Sn30 at high temperatures

Type-I clathrate Ba₈Ga₁₆Sn₃₀ is known as a typical example showing glass-like behavior in the thermal conductivity at low temperatures. We report on thermoelectric properties above room temperature for the p- and n-type single crystals which were grown from Ga–Sn double flux and Sn single flux, respectively. The measurements of electrical resistivity showed hysteretic behaviors when the sample was heated to 600 K. Powder X-ray diffraction analysis indicated that the type-I structure changed to the type-VIII after the sample was heated to 600 K. By using the data of Seebeck coefficient, electrical resistivity, and thermal conductivity, we estimated the dimensionless figure of merit ZT for the type-I Ba₈Ga₁₆Sn₃₀. For the p- and n-type samples, the values of ZT reach 0.58 and 0.50 at around 450 K, respectively, which values are approximately half of those for the type-VIII counterparts.     

InSe electrical characterization by means of transport parameters

SCLC measurements in single crystals of the layered semiconductor n-type InSe are reported. The measurements were carried out at various temperatures and on samples grown with indium added in excess (from 5 to 10%). The experimental results suggest that the trapping levels location and the charge transport are dependent on the indium excess. Only the samples grown with an indium excess of about 5% show the features typical of intrinsic semiconductors. The anomalous behaviour of samples grown with indium excess between 6 and 10 is explained by means of scattering mechanisms between charge carriers and ionized impurity centers.     

Changes in optical absorption in iron garnet films due to impurity incorporation

The incorporation of impurities in films of Bi-substituted iron garnets grown by liquid phase epitaxy has been studied by successively adding small amounts of SiO₂ and CaCO₃ to the melt before film growth. It is found that very small additions of CaCO₃ to the melt profoundly influences the optical absorption coefficient and the electrical properties. The impurity absorption ofn-type YIG doped with Si⁴⁺ and Pb²⁺ ions is investigated and its wavelength dependence compared to that ofp-type YIG. The optical transitions involved in the impurity absorption of iron garnets are discussed in terms of transition reaction, photon energy and dependence on the impurity concentration. Depending on the photon energy, one or several transitions may give rise to impurity absorption.     

Reactivity of ZnO: Impact of polarity and nanostructure

The effects of atomic hydrogen and nitrogen produced by remote r.f. H₂ and N₂ plasmas on the structure, morphology, and optical and electrical properties of Zn- and O-polar ZnO crystals and on ZnO thin films grown by metal–organic chemical vapour deposition (MOCVD) have been studied. It is found that the Zn-polar form is highly reactive with atomic hydrogen, while the O-polar form is almost inert. This difference in reactivity allows one to discern the O-polarity of the (0001) oriented ZnO thin films grown by MOCVD. A decrease of the resistivity of the grain-like MOCVD films is found upon atomic hydrogen treatment. Conversely, atomic nitrogen treatment results in p-type doping of the ZnO film and in an improvement of the surface morphology and microstructure.     

Electrical properties of Cd,Zn and S ion-implanted layers in GaAs

The electrical properties of cadmium, zinc, and sulfur ion-implanted layers in gallium arsenide have been measured by the van der Pauw-Hall technique. Ion implantation was performed with the substrates held at room temperature. The dependence of sheet resistivity, surface carrier concentration, and mobility on ion dose and on post-implantation anneal temperature was determined. In the case of 60 keV Cd⁺ ions implanted into n-type substrates, a measurable p-type layer resulted when samples were annealed for 10 minutes at a temperature in the range 600—900°C. After annealing at 300—900°C for 10 minutes, 100 per cent electrical activity of the Cd ions resulted for ion doses ≤ 10¹⁴/cm².

The properties of p-type layers produced by implantation of 85 keV Zn⁺ ions were similar to those of the 60 keV cadmium-implanted layers, in that no measurable p-type behavior was observed in samples annealed below a relatively high temperature. However, in samples implanted with 20 keV Zn⁺ ions a p-type layer was observed after annealing for 10 minutes at temperatures as low as 300°C.

Implantation of sulfur ions into p-type GaAs substrates at room temperature resulted in the formation of a high resistivity n-type layer, evcn before any annealing was performed. Annealing at temperatures up to 200°C or above 600°C lowered the resistivity of the layer, while annealing in the range 300—500°C eliminated the n-type layer.     

Copper-assisted shape control in colloidal synthesis of indium oxide nanoparticles

Indium oxide is an important n-type transparent semiconductor, finding application in solar cells, sensors, and optoelectronic devices. We present here a novel non-injection synthesis route for the preparation of colloidal indium oxide nanocrystals by using oleylamine (OLA) as ligand and as solvent. Indium oxide with cubic crystallographic structure is formed in a reaction between indium acetate and OLA, the latter is converted to oleylamide during the synthesis. The shape of the nanocrystals can be influenced by the addition of copper ions. When only indium (III) acetate is used as precursor flower-shaped indium oxide nanoparticles are obtained. Addition of copper salts such as copper (I) acetate, copper (II) acetate, copper (II) acetylacetonate, or copper (I) chloride, under otherwise identical reaction conditions changes the shape of nanoparticles to quasi-spherical or elongated. The anions, except for chloride, do not influence the shape of the resulting nanocrystals. This finding suggests that adsorption of copper ions on the In₂O₃ surface during the nanoparticles growth is responsible for shape control, whereas changes in the reactivity of the In cations caused by the presence of different anions play a secondary role. X-ray diffraction, transmission electron microscopy, nuclear magnetic resonance, energy dispersive X-ray analysis, and UV–Vis-absorption spectroscopy are used to characterize the samples.     

Surface potential images of polycrystalline organic semiconductors obtained by Kelvin probe force microscopy

P-type copper phthalocyanine (CuPc) and n-type hexadecafluorophthalocyanina-tocopper (F₁₆CuPc) polycrystalline films were investigated by Kelvin probe force microscopy (KPFM). Topographic and corresponding surface potential images are obtained simultaneously. Surface potential images are related with the local work function of crystalline facets and potential barriers at the grain boundaries (GBs) in organic semiconductors. Based on the spatial distribution of surface potential at GBs, donor- and acceptor-like trapping states in the grain boundaries (GBs) of p-CuPc and n-F₁₆CuPc films are confirmed respectively. In view of spatial energy spectrum in micro-scale provided by KPFM, it is going to be a powerful tool to characterize the local electronic properties of organic semiconductors.     

Electrically active defect annealing in neutron and in ion-damaged Si

Hall effect and electrical conductivity measurements of defect annealing in 1 ohm-cm n-type and 2 ohm-cm p-type silicon were made following neutron irradiation at ～50°C. Measurements were also made following 400-keV B¹¹ ion implantation into a 100 ohm-cm n-type Si substrate. As the neutron fluence is increased the electrical effects of the damage eventually outweigh those of the chemical dopants, and further changes in the electrical properties become small. Conversely, significant electrical recovery upon annealing begins only when the electrical effects of the remaining damage become comparable to those of the chemical dopants. This condition will occur at higher anneal temperatures for higher fluence irradiations. The neutron fluence dependence of the damage and the annealing is interpreted in terms of the neutron energy per cm³. E, spent in atomic processes divided by the number/cm³, N, of electrically active dopants. When E/N ≤ 0.5 keV the electrical measurements show that the predominant defect annealing occurs below 400°C. However, when E/N > 0.5 keV electrical measurements emphasize the annealing at temperatures > 400°C. After 500°C annealing, energy levels in neutron damaged Si are observed at E_v +0.1 and E_v +0.15 eV in p-type and at E_c -0.33 eV in n-type Si. Application of the E/N criteria to room temperature implant-doped Si predicts that the electrical effects will be dominated by lattice damage even if all the implanted ions are substitutional.     

Effect of annealing on the electrical properties of nitrogen-doped silicon single crystals grown by crucibleless zone melting

The electrical properties of nitrogen-doped silicon single crystals of the n and p types grown by crucibleless zone melting and annealed at 680°C have been studied. It is shown that the annealing brings about the appearance, in the crystals, of nitrogen-containing centers, which form deep donor and acceptor levels in the band gap. The process is accompanied by an increase in the electrical resistivity; the increase is particularly substantial in the initially high-resistance single crystals. On the other hand, in slightly boron-doped single crystals of the n and p types, the conversion of the conduction type is observed. In a converted material of the n-type, the electron mobility is anomalously low, which demonstrates its high electrical spatial inhomogeneity. The energy of the deep acceptor level near E _c ? 0.35 eV introduced during annealing has been determined. The model explaining the phenomena observed is proposed.     

Effect of electron irradiation on the galvanomagnetic properties of In<Subscript>x</Subscript>Bi<Subscript>2−<Emphasis Type="Italic">x</Emphasis></Subscript>Te<Subscript>3</Subscript> semiconductor single crystals

The effect of 5-MeV electron irradiation of p-In_xBi_2?xTe₃ single crystals (x=0, 0.04, 0.07), performed at 250 K, on the galvanomagnetic properties of the crystals was studied. The irradiation was shown to change the conduction from the p to the n type. Annealing at temperatures of 310–390 K restores the conduction to the p type. The reversal of the conduction type and variation of the carrier concentration can be accounted for by an increase in the concentration of charged point radiation defects produced in In_xBi_2?xTe₃ by irradiation. Electron irradiation of p-type Te single crystals reduces the electrical resistivity without reversing the conduction type. Annealing restores the original properties almost completely.     

Magnetic and electrical properties of cation-substituted sulfides MexMn1 ? xS (Me = Co, Gd)

The temperature dependences of the specific magnetization σ and the electrical resistivity ρ of Me _x Mn_{1 − x} S single crystals (Me= Co, Gd; x= 0.05) have been studied in the temperature range 80 K < T < 1000 K. The samples under study have revealed the presence of a spontaneous magnetic moment below the Néel temperature (T _N) and ferromagnetic clusters in Gd_0.05Mn_0.95S in the temperature range 146 K < T < 680 K. Substitution of gadolinium for manganese initiates a transition from p-type to n-type conduction. The change in the conduction type is accompanied by an increase in the electrical resistivity at 300 K by approximately one order of magnitude and, accordingly, by a decrease in the activation energy. The magnetic and electrical properties of the crystals under study have been interpreted in terms of the cluster model with temperature-dependent ferromagnetic exchange and an electron localized in this cluster. Original Russian Text ? S.S. Aplesnin, L.I. Ryabinkina, O.B. Romanova, V.V. Sokolov, A.Yu. Pichugin, A.I. Galyas, O.F. Demidenko, G.I. Makovetskiĭ, K.I. Yanushkevich, 2009, published in Fizika Tverdogo Tela, 2009, Vol. 51, No. 4, pp. 661–664.     

Lifetime spectra of positrons in deformed Ge

Positron lifetime measurements have been performed inn-type andp-type germanium single crystals deformed by compression. The results are compared with those of deformed GaAs single crystals obtained by the authors previously. In bothn andp-type germanium the lifetime τ₁ and its intensityI ₁ decreased with deformation. Using the trapping model, the trapping rates of positrons by dislocations are obtained, which in turn gave the cross width of the dislocation as 20.0 Å and 8.2 Å forn-type andp-type germanium, respectively. In terms of Read's model the fraction of the dangling bonds occupied by electrons is obtained to 0.26 in then-type germanium. This value was smaller than those obtained forn-type GaAs, i.e., 0.46 and 0.50 for Ga- and As-dislocation, respectively. It is found that doping causes the trapping of positrons. Inp-type germanium the fractionf was determined to 0.25 in terms of Schröter and Labusch's model.     

Impedometric anion sensing behaviour of InxGa1 − xN films grown by modified activated reactive evaporation

In the present work, In_xGa_{1 − x}N films with different indium compositions (x = 0.88, 0.63, 0.36 and 0.18) were prepared on glass substrates using a commercially viable technique known as modified activated reactive evaporation. Electrochemical impedance was used to investigate the anion sensing properties of these films for KCl, KI and KNO₃ salt solutions of different molar concentrations. The anion sensing behaviour of InGaN films is attributed to the presence of high n-type background carrier concentration and positively charged surface donor states. The InGaN based anion sensors were found to have good sensitivity with faster response and recovery time. The film with x = 0.63 was found to have the highest sensitivity for all the anions due to the presence of more active surface area together with large number of surface donor states.     

Electrical characterization studies of p-type Ge,Ge1−ySny,and Si0.09Ge0.882Sn0.028 grown on n-Si substrates

The electrical properties of p-type Ge, Ge_1−ySn_y, and Si_0.09Ge_0.882Sn_0.028 samples grown on n-type Si substrates using ultra-high vacuum chemical vapor deposition have been investigated as a function of temperature. Degenerate parallel conducting layers were found in all Ge/Si, Ge_1−ySn_y/Si, and Si_0.09Ge_0.882Sn_0.028/Si samples, which are believed to be associated with dislocation defects at the interface produced by the lattice mismatch between the two materials. These degenerate conducting layers affect the electrical properties of all the thin epitaxial films. Additionally, temperature dependent Hall-effect measurements show that these materials exhibit a conductivity type change from p to n at around 370–435 K. The mobilities of these samples are generally lower than that of bulk Ge due to carrier scattering near the interface between the epitaxial layer and the Si substrate and also due to alloy scattering. Detailed behavior of temperature-dependent conductivity of these samples is also discussed.     

Effect of pressure on electrical properties of SnS x Se1−x single crystals

The single crystals of tin monosulphoselenides in the form of a series SnS _x Se_1?x (where x?=?0, 0.25, 0.50,0.75 and 1) have been grown using the direct vapor transport technique (DVT). The analysis of the X-ray diffraction patterns reveals that all crystals belong to the orthorhombic crystal structure. Hall effect measurements were carried out on grown crystals at room temperature. The optical absorption measurements at room temperature have been carried out for all crystals. The values of the band gap were determined at atmospheric pressure and also calculated at high-pressure. Simultaneous thermoelectric power (TEP) and a.c. resistance measurements up to 8?GPa were carried out. The results of the effect of high-pressure on the electrical resistance of the grown crystals are reported in this paper.     

Role of zinc and nickel impurities in high-temperature superconductors

The local changes produced in the electronic structure and their effect on the physical properties of the superconducting and normal phases when zinc and nickel are substituted for copper are examined on the basis of a multiband p-d model. It is shown that strong electronic correlations suppress the S=1 configuration of Ni²⁺ and cause the superposition of the S=1/2 and S=0 states of nickel. The change in the density of states in p-and n-type systems is studied, and the peculiarity of Zn impurity for p-type systems and Ni impurity for n-type systems is shown. The universal dependence of the T _c on the residual resistance in lightly doped superconductors and deviations from it in optimally doped systems are discussed. Fiz. Tverd. Tela (St. Petersburg) 41, 596–600 (April 1999)     

Electric performance and photosensitivity of heterostructures prepared by thermal decomposition of a gallium nitrate aqueous solution on an indium selenide (0001) cleaved surface

It is shown that thermal decomposition of a gallium nitrate aqueous solution on the surface of a semiconductor in air can basically be used for preparing structures sensitive to radiation from in the near-UV spectral range. The electric and photovoltaic properties of Ga₂O₃-n-(p-)InSe heterostructures are studied. It is found that a high-ohmic layer arising at the InSe-Ga₂O₃ interface affects not only the electric performance but also the photoelectric spectra of the heterostructures. It is supposed that current instability with Z- and N-shaped reverse branches in the I-V characteristics of the Ga₂O₃-p-InSe structures stems from doping nonuniformity in the bulk of quasi-two-dimensional p-type indium selenide.     

Thermostatistical properties of a q-deformed bosonic exciton gas

We present the calculations of the electronic structure and transport properties on the filled-skutterudites LaFe₄Sb₁₂ and CeFe₄Sb₁₂ using the full-potential linearized augmented plane-wave method and the semi-classical Boltzmann theory. Our calculation indicates that LaFe₄Sb₁₂ and CeFe₄Sb₁₂ have the large density of states near the Fermi level. The obtained Seebeck coefficient and the magnetic susceptibilities are in good agreement with experimental results. It is found that n-type doping in the CeFe₄Sb₁₂ compound may be more favorable than p-type doping below 900 K and p-type doping in the CeFe₄Sb₁₂ compound may be more favorable than n-type doping above 900 K. It is also seen that n-type doping in the LaFe₄Sb₁₂ compound may be more favorable than p-type doping below 700 K and p-type doping in the LaFe₄Sb₁₂ compound may be more favorable than n-type doping above 700 K. Ultimately, we found that LaFe₄Sb₁₂ is more suitable for thermoelectric applications than CeFe₄Sb₁₂.     

关于ZnSe—ZnS应变超晶格P型导电机理的探讨

本文利用变温Hall测量,证实了我们用MOCVD法生长的No.87—39A ZnSe-ZnS应变超品格(SLS)具有P型导电特性。文中试图从应变超晶格的临界厚度,电学参数、能带结构等方面解释ZnSe-ZnS SLS反型的原因。文中指出,这时的受主能级可能处于ZnS层靠近界面附近,这些受主能级的位置比ZnSc阱中满带顶能量低。