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1.
Se85Te10Bi5 films of different thicknesses ranging from 126 to 512 nm have been prepared. Energy-dispersive X-ray (EDX) spectroscopy technique showed that films are nearly stoichiometric. X-ray diffraction (XRD) measurements have showed that the Se85Te10Bi5 films were amorphous. Electrical conduction activation energy (ΔEσ) for the obtained films is found to be 0.662 eV independent of thickness in the investigated range. Investigation of the current voltage (I-V) characteristics in amorphous Se85Te10Bi5 films reveals that it is typical for a memory switch. The switching voltage Vth increases with the increase of the thickness and decreases exponentially with temperature in the range from 298 to 383 K. The switching voltage activation energy (ε) calculated from the temperature dependence of Vth is found to be 0.325 eV. The switching phenomenon in amorphous Se85Te10Bi5 films is explained according to an electrothermal model for the switching process. The optical constants, the refractive index (n) and the absorption index (k) have been determined from transmittance (T) and reflectance (R) of Se85Te10Bi5 films. Allowed non-direct transitions with an optical energy gap (Egopt) of 1.33 eV have been obtained. ΔEσ is almost half the obtained value of Egopt, which suggested band to band conduction as indicated by Davis and Mott.  相似文献   

2.
On annealing p-type CdTe, considerable change in conductivity takes place. Samples of high resistivity were used for the measurements. Each of a set of samples was annealed at different temperature. After annealing, the temperature dependence of the conductivity and the relaxation curves of the photoconductivity were measured. Analysis of the first set of curves yielded value of energyE a corresponding to the level occurring in given samples. It was established that this acceptor level is due to Vcd, or Vcd complexes, and is situated at 0.3 eV above the valence band edge. Concentration of these levels is increased by annealing. Furthermore, an energy value ofH=0.79 eV was found, corresponding very probably to the formation energy of a vacancy Vcd.Analysis of the relaxation curves yielded the temperature dependence of S , T and the energy distanceE M of the impurity level that is responsible for photoconductivity. A value of (E g -E M )=0.09–0.12 eV was found for all samples studied. This level therefore lies below the conduction band edge and its concentration amounts to 1014–1015 cm–3. The level is probably due to foreign impurities.Two sets of samples were used: both as-grown and Sb-doped. The results for both sets were not much different from each other.Ke Karlovu 3, Praha 2, Czechoslovakia.  相似文献   

3.
We present the results of studies on the influence of deep levels, due to dislocations in electronic-grade silicon, on the lifetime of minority carriers and on the current-voltage and capacitance-voltage characteristics of p-n junctions. The parameters of the deep levels were determined by means of dynamic spectroscopy. The carrier lifetime in the high-resistance region of the p-n junction correlates well with the dislocation density and varies from 10–7 sec to 3 · 10–8 sec when the dislocation density Nd varies from 107 cm–2 to 5 · 103 cm–2. The voltage across the p-n junction at a high level of injection varies 1.6 to 6.2 v as a function of Nd. The ionization energy of deep levels associated with dislocation in silicon is 0.44 and 0.57 eV, measured from the bottom of the conduction band.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 81–84, January, 1988.  相似文献   

4.
The dependences of the path of leading dislocations in indentation rosette rays on the load, the loading time, and the indentation temperature in the range 260 < T ≤ 373 K were studied for C60 fullerite crystals. The dislocation mobility parameters are estimated: the exponent m characterizing the stress dependence of the dislocation velocity depends on the structural perfection of the crystal and ranges from 2.3 to 24.5, the activation energy for dislocation motion ΔH 0 ? (0.4–0.5) eV, and the velocity of leading dislocations in indentation rosette rays v l ? 10?5?10?4 cm/s. The data from micro-and macromechanical experiments are shown to agree with each other. The dislocation mobility is assumed to be controlled by the dislocation interaction with local barriers.  相似文献   

5.
The photoluminescence, photoconductivity and absorption in GaSe0.9Te0.1 alloy crystals have been investigated as a function of temperature and external electric field. It has been observed that the exciton peaks shift to lower energy in GaSe0.9Te0.1 alloy crystals compared to GaSe crystals. The long wavelength tails of interband photoluminescence, photoconductivity and absorption spectra are determined by the free exciton states and show an Urbach-Martienssen-type dependence to the photon energy. The maxima of the extrinsic photoluminescence and photoconductivity spectra were found to be determined by the acceptor centers with an energy of EA=EV+0.19 eV formed by the polytypism and defects complexes that include Se and Te anions.  相似文献   

6.
Tunneling measurements of dI/dV, d 2 I/dV 2, and d 3 I/dV 3 were formed along the C 3 axis (normally to layers) for Bi2Te3 and Sb2Te3 layered semiconductors in the temperature range 4.2<T>29 5 K. Temperature dependences of the forbidden band energy E g were obtained. The forbidden band energy in Bi2Te3 was 0.20 eV at room temperature and increased to 0.24 eV at T=4.2 K. The E g value for Sb2Te3 was 0.25 eV at 295 K and 0.26 eV at 4.2 K. The distance between the top of the higher valence band of light holes and the top of the valence band of heavy holes situated lower was found to be ΔE V≈19 meV in Bi2Te3; this distance was independent of temperature. The conduction bands of Bi2Te3 and Sb2Te3 each contain two extrema with distances between them of ΔE c≈25 and 30 meV, respectively.  相似文献   

7.
Recent measurements on halogen doped CdTe shows an unidentified electron trapping level at 0.05 eV. Using a mass action approach to self compensation involving a substitutional halogen, XTe, and a cadmium vacancy, VCd, it can be shown that in addition to the two-defect complex, VCdXTe, the three-defect complex (VCd2XTe) is present in substantial concentrations. A calculation of the binding energy of an electron to this three-defect-complex using the configurational interaction and one electron wave function, leads to a bound state with a depth about right for the unidentified level.  相似文献   

8.
A comparative study of the temperature dependence of electrical resistivity, carrier concentration and carrier mobility of the Ordered Defect Compounds (ODCs) CuIn3Se5, CuIn3Te5, and CuIn5Te8 with their corresponding normal 1:1:2 phase is reported. Relatively lower carrier concentration and higher activation energy observed in ODCs is explained on the basis that shallow acceptor or donor levels observed in 1:1:2 phase are partially annihilated in these compounds due to attractive interaction between VCu−1 and InCu+2 defect pair. In the activation regime, the mobility is explained by taking into account a scattering mechanism of the charge carriers with donor–acceptor defect pairs. The electrical data at lower temperatures is explained with the existing theoretical expression for the nearest neighbor hopping conduction mechanism.  相似文献   

9.
Deep Level Transient Spectroscopy (DLTS) and Optical Deep Level Transient Spectroscopy (ODLTS) experiments have been conducted on a series of In-doped CdTe crystals grown by the Bridgman or the travelling heater (THM) methods using Te as the solvent. The THM samples are n-type but strongly compensated. Annealing at 700°C under high Cd vapour pressure leads to a decompensation of the crystals. The electron concentration is then a measure of the donor (In) concentration, which was in the range 3 × 1016−1.5 × 1018cm−3. Six and eight electron traps are, respectively detected in the non-annealed and annealed samples at a concentration level 102–103 times below the net electron concentration. They cover the energy range 0.2–0.8 eV. Similar traps are found in both types of crystals, the concentration of which increases with In content and after annealing. The presence of In interstitial-type defects is suggested. A main hole trap at 0.12eV is detected by ODLTS in compensated samples with a concentration close to the donor concentration. Low temperature electrical measurements show that this trap is ionized under equilibrium conditions. It appears to be the main compensating acceptor centre. A plausible microscopic structure is IncdVcd. This study shows that In-doped CdTe grown by THM is electrically compensated and that In-containing neutral associates or precipitates play a minor role in the compensation mechanism.  相似文献   

10.
Samples of n-type germanium with a donor concentration N d=2.4×1016 cm−3 are plastically deformed to a degree of strain equal to 18–40% to detect static conduction by electrons trapped on dislocations in a system of dislocation grids. In samples with 20%<δ<31%, which retain an electronic type of conductivity, the conductivity for T<8 K, which is weakly temperature-dependent, is associated with conduction by electrons trapped on dislocations. The nonmonotonic dependence of the conductivity at 4.2 K on the degree of strain as the latter increases from 18% to 40% attests to the existence of an energy gap between the donor and acceptor dislocation states in strongly plastically deformed germanium. Zh. éksp. Teor. Fiz. 115, 115–125 (January 1999)  相似文献   

11.
Experiments are presented to establish that irradiation produced defects in lead not only pin dislocations but also can be trapped at the ends of dislocation lines in agreement with the model proposed by Thompson, Buck, Huntington and Barnes. This model indicates that there is a temperature T* at which there is a maximum pinning of dislocations. T* is found to be near 140 K. The data of Part I are analyzed according to this model using reasonable values of the dislocation density and the binding energy of the defect in the trap. The resulting activation energy for the region A process in the reaction kinetics model is found to be 0.15 eV which is consistent with the value found from an eigenvalue expansion model.  相似文献   

12.
The results of an in situ mass-spectrometric study of surface processes occurring during CdTe molecular beam epitaxy are presented. The measurements of kinetic parameters are performed with modulated Cd and Te2 molecular beams with an intensity of 0.1–5.0 ML/s at a crystal temperature of 550–730 K. The experimental results are treated using a model in which condensation and evaporation proceed through adsorption and desorption steps. The desorption rates are 2–15 and 150 s?1 for Te2 and Cd, respectively. The activation energy of CdTe “evaporation” is found to be 1.2 eV; the desorption energies are E d(Cd) = 1.0 eV and E d(Te2) = 0.3 eV. The adsobate coverage with cadmium atoms and tellurium molecules is estimated to be n(Cd) < 0.01, n(Te2) = 0.02–0.20, and n(Te) = 0.2–1.0.  相似文献   

13.
Optical detection of magnetic resonance (ODMR) is reported for the single negative charge state, VZn?, of the isolated zinc vacancy in ZnS. Produced by 2.5 MeV electron irradiation, it is detected in a distant donor-acceptor (DA) pair luminescent band at 570 nm in which the vacancy acts as the acceptor. Excitation and emission spectral dependences of the VZn? ODMR signals are analyzed in terms of a configurational coordinate model. We conclude that the double acceptor level (VZn=/VZn?) is located ~1.1 eV from the valence band edge and that the trigonal Jahn-Teller relaxation energy for the VZn? state is ~0.5 eV.  相似文献   

14.
Electrical conductivity and thermopower measurements are reported for the defect semiconductors p-In2Te3 and n-Ga2Te3. The hole mobility μp in the former varied as Tnwheren=+5.98 forT<350 K and n=-4.13 forT>350 K showing a maximum of 210 cm2V-1 sec-1 at 350 K. Electron mobility in n-Ga2Te3 also went through a maximum at 320 K. The optical band-gaps for both were found to be direct, with values of 1.01 and 1.08 eV for In2Te3 and Ga2Te3 respectively at 300 K. Pronounced effects of annealing on TEP and optical absorption gave evidence of defect ordering at low temperatures followed by defect creation at T>350 K.  相似文献   

15.
A new method of studying the energy characteristics of dislocations is proposed, which is based on the investigation of the interaction of moving dislocations with purposefully introduced electronic and hole centers. A study has been made of KCl, NaCl, KBr, LiF, and KI alkali halide crystals containing electronic F and hole V K and Me ++ (Cu++, Ag++, Tl++, In++) centers. Investigation of the temperature dependence of the dislocation interaction with the F centers permitted determination of the position of the dislocation-induced electronic band (DEB) in the band diagram of the crystal. In KCl, the DEB is separated by ≈2.2 eV from the conduction-band minimum. It is shown that dislocations transport holes from the centers lying below the dislocation-induced hole band (DHB) (X +, In++, Tl++, V K) to those above the DHB (the Cu+ and Ag+ centers). Such a process is temperature independent. The DHB position in the crystal band diagram has been determined; in KCl it is separated by ≈1.6 eV from the valence-band top. The effective radii of the dislocation interaction with the electronic F and hole X +, V K, and Tl++ centers have been found. Fiz. Tverd. Tela (St. Petersburg) 41, 2139–2146 (December 1999)  相似文献   

16.
Under nitrogen-rich growth conditions, the present ab initio study predicts that hydrogen passivation is more effective on the acceptor Be instead of Mg in a co-doped p-type GaN. The formation energy is 0.24 eV for (H-BeGa) complex, and 0.46 eV for (H-MgGa) complex. Congruently, the binding energy is 1.40 eV for (H-BeGa), and 0.60 eV for (H-MgGa). Owing to the lower binding energy, (H-MgGa) is not thermally stable. As Be is incorporated in Mg-doped GaN, a (H-MgGa) may release a H+ cation at relatively elevated temperatures. Consequently, the H+ diffuses swiftly away from a MgGa, across a barrier of 1.17 eV, towards a BeGa and forms a stable (H-BeGa) with it. The activation of Mg acceptors can be thus facilitated. In this view, the process of hydrogen depassivation of the Mg acceptor by Be can convert the as-grown high-resistivity Mg-doped GaN into a p-conducting material, as observed in the experiments.  相似文献   

17.
Surface processes in CdTe molecular-beam epitaxy were studied using in situ mass spectrometry. Modulated molecular Cd and Te2 beams were used for measuring kinetic parameters. The experiments were performed at crystal temperatures of 600–730 K. The results were processed within a model in which condensation and evaporation occur through adsorption and desorption stages. The desorption rate was 2–10 s?1 for Te2 and more than 30 s?1 for Cd. The CdTe evaporation activation energy and desorption energies were determined as E ev = 1.1 eV, E d (Cd) = 1.0 eV, and E d (Te) = 0.6 eV. The adsorbate coverage was estimated as n(Cd) < 0.01 and n(Te) = 0.1–1 Te.  相似文献   

18.
The activation energy of the hopping frequency of the vanadium-3d 1-electron is derived from the temperature dependence of the ESR linewidth in the following semiconducting, pentavalent vanadium-compounds: NaxV2O5, LixV2O5 (x <0.02), V2O5 weakly doped with WO3 or MoO3 (E a ≈0.07 eV). In V2MoO8, vanadium-3d 1-electrons are responsible for the electronic conductivity, too.  相似文献   

19.
P doped ZnO films were grown on quartz by radio frequency-magnetron sputtering method using a ZnO target mixed with 1.5 at% P2O5 in the atmosphere of Ar and O2 mixing gas. The as-grown P doped ZnO film showed n-type conductivity, which was converted to p-type after 800 °C annealing in Ar gas. The P doped ZnO has a resistivity of 20.5 Ω cm (p∼2.0×1017 cm−3) and a Hall mobility of 2.1 cm2 V−1 s−1. XRD measurement indicated that both the as-grown and the annealed P doped ZnO films had a preferred (0 0 2) orientation. XPS study agreed with the model that the PZn-2VZn acceptor complex was responsible for the p-type conductivity as found in the annealed P-doped ZnO. Temperature-dependent photoluminescence (PL) spectrum showed that the dominant band is located at 3.312 eV, which was attributed to the free electronic radiative transition to neutral acceptor level (FA) in ZnO. The PZn-2VZn acceptor complex level was estimated to be at EV=122 meV.  相似文献   

20.
The magnetoplastic effect in dislocation silicon is discovered. It is shown that in the presence of tensile stresses (up to 20 MPa), the mechanically activated path of surface dislocation half-loops is limited mainly by the dynamics of defects in various slip systems relative to the applied load. The activation barriers for the motion of dislocations controlled by various conditions in the temperature range T=850–950 K are E aF=2.1±0.1 eV and E aS=1.8±0.1 eV. An increase in the path of surface dislocation half-loops and a change in the activation barriers are detected (E aF=1.4±0.1 eV and E aS=1.6±0.1 eV) after subjecting silicon to a magnetic field (B=0.7 T) for 30 min. Possible reasons behind the observed effects are discussed.  相似文献   

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