Electrical breakdown in ZnS:Mn films grown by rf-magnetron sputtering

We have studied the electrical breakdown field strength E_br of ZnS films doped with Mn(ZnS:Mn), produced by rf magnetron sputtering, as a function of film thickness d in the system Al-ZnS:Mn-Al. Electron-microscope studies have shown that breakdown is initiated under inhomogeneous field conditions imposed both by the roughness of the aluminum electrode and by the polycrystallinity of the ZnS:Mn film. An observed increase in E_br as d is reduced below 0.7 µm, with no polarity effect in breakdown under dc field conditions, is explained in terms of an electron-thermal breakdown model.Institute for Automation and Radio Electronics, Tomsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 41–44, March, 1993.     

Investigation of the electrical and photoelectric properties of manganese-doped gallium arsenide as a material for photoresistive detectors

An investigation was made into the electrical and photoelectric properties of gallium arsenide with an initial electron density 5×10¹⁵–4×10¹⁷ cm^–3 doped with Mn in different thermodynamic diffusion regimes characterized by diffusion temperatures of 900 and 1000°C and arsenic vapor pressure 10^–2 and 10^–3 atm. The ionization energy and defect concentration were determined by a computer analysis of the equilibrium hole density determined from the Hall effect. Centers with ionization energy 0.08–0.10 eV were found, their concentration varying from 2×10¹⁹ to 2×10²⁰ cm^–3 depending on the diffusion temperature and the doping level of the original crystals. Data obtained by investigating the stationary intrinsic photoconductivity were used to determine a hole lifetime of t_p 10^–9 sec. The photoconductivity spectra were investigated in the range 0.5–2 eV at 77°K, and defects with ionization energy E_v + 0.6 eV were found in all samples. The impurity photoconductivity at wavelength 10.6 m was investigated. It was shown that GaAsMn can be used as a material for impurity photoresistors.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 15–19, March, 1981.     

Annealing behavior ot trap-centers in silicon containing A-swirl defects

The annealing behavior of trap-centers was studied in float-zone silicon wafers containing A-swirl defects. Samples from areas of high and low A-swirl density were annealed in nitrogen ambient between 100° and 900 °C, and analysed using the Deep Level Transient Spectroscopy. The results indicate, that two levels atE _c }-0.07 eV, _n=4.6×10^–16 cm², andE _c–0.49eV, _n=6.6×10^–16cm² are caused by one defect, for which the silicon di-selfinterstitial is a likely interpretation. A level atE _c }-0.11 eV was assigned to interstitial carbon. Both defects annealed out at about 170 °C. After 600 °C annealing an additional level atE _c–0.2 eV was detected, which was attributed to an interstitial silicon carbon complex. Heat treatment at 800 °C generated a new level atE _c–0.49 eV, _n=2.9×10^–16cm² only in the area of high A-swirl defect density. This level was also observed after oxidation and subsequent annealing of silicon.     

Annealing of radiation-induced defects in ion-implanted AIIBVI single crystals

The basic characteristics of annealing of implanted layers of A^II-B^VI compounds are studied. The equilibrium, quasiequilibrium, and nonequilibrium methods of annealing were employed. Equilibrium annealing was conducted in the saturated vapor of the metalloid at temperatures below the critical temperature, above which intense self-compensation processes start (T_cr 450–500°C for ZnS and ZnSe). If T_ann must be higher than T_cr owing to radiation-induced damage that is difficult to anneal, than the method of annealing under an active protective film was employed. For ZnSe and ZnS with an implanted acceptor impurity the protective film consisted of gold or silver sputtered on the crystal prior to annealing. Thus implantation of ions enabled obtaining layers of p-type ZnS with resistivities of 10²–10³ ·cm. The ZnSe layers with hole conductivity were also obtained with electron annealing under a protective gold film with weak-current beams with durations of several seconds. Quasiequilibrium annealing was conducted in the activated vapor of the metalloid. The vapor was activated by a high-frequency discharge in the vapor of the metalloid. This method of annealing gave sharp p-n junctions on implanted ZnSe. Pulsed electron beams were employed for nonequilibrium annealing.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 51–56, March, 1989.     

Electrophysical properties of ionic alloys of GaAs obtained by implanting Zn+ (150 keV) with subsequent annealing at 500–1000°C

A study is made of the electrophysical properties (N_s, _eff) of ionic alloys of GaAs obtained by implanting 150-keV Zn ions at 20 and 300°C. The ion dose D=5·10¹³–10¹⁶ ions/cm²; the alloys were subsequently annealed for 10 min in an H₂ atmosphere with temperatures in the range 500–1000°C. The optimal parameters of the ionic alloys are obtained for T_i=300°C and T_a=700°C. Thermal acceptance of the GaAs under a SiO₂ film (d0.2–0.3 m) is observed for T_a>700°C. The limiting concentration of thermal acceptors N_s(TA)3·10¹³ cm^–2) for T=1000°C and t=10 min.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 22–26, March, 1979.     

Trap centers in Au-implanted MOS structures

Trap centers in the Si-SiO₂ interface region of MOS structures doped by ion implantation of gold have been investigated using constant capacitance deep level transient spectroscopy (CC-DLTS). Gold doses of 10¹²–3 × 10¹³ cm^–2 were implanted into the back surface of the wafers and were then redistributed during a diffusion anneal for 30 min at 1100° or 900° C. Three Au-related trap levels have been observed in the interface region, which were attributed to the Au-donor (E _v +0.35 eV), the Au-acceptor (E _v +0.53 eV), and the Au-Fe complex (E _v +0.45 eV). The trap concentration profiles show that the Si-SiO₂ interface affects the Au concentration in a depth range of 1 m from the interface and that gettering of Au occurs at the interface. The interface state density is independent of the Au concentration at the interface even for concentrations of 10¹⁵ cm^–3.     

Diffusion of Al in ion-implanted Pd and Pt

The diffusion coefficients of aluminium have been measured in polycrystalline fcc Pd and Pt. The Al-implanted palladium and platinum samples were annealed at 400°–800 °C and 450°–900 °C, respectively. The aluminium profiles were probed using the nuclear resonance broadening (NRB) technique. Values of (1.41±0.09) and (1.38±0.09) eV for the activation energy and (1.5 _–1.0 ⁺⁵ )×10^–6 and (4 _–3 ⁺¹⁰ )×10^–7cm²/s for the frequency factor were obtained for Al in Pd and Pt, respectively. These anomalous results, compared to the normal impurity diffusion, were checked using also Al-evaporated samples.     

Rates of change in high temperature electrical resistivity and oxygen diffusion coefficient in Ba2YCu3Ox

The change in electrical resistance with time for bulk, thick-film, and thin-film Ba₂YCu₃O_x at atmospheric pressure is described as a function of the oxygen partial pressure (100 to 0.001%) and temperature (320°–750°C). The potential usefulness of these materials as oxygen sensors is demonstrated. The rate of equilibration is faster during oxygen uptake than during its loss. Time constants to reach equilibration (1/e remaining), qualitatively scale with sample dimensions. For a 1m film at 600° C, <1 s for the range of P_O2 (O2 being a shorthand for O₂) from 100% to 0.001%. The rate increases markedly with increasing P_O2. The actual resistance decreases with P_O2 at a rate of log/log P_O2 = 0.4 at 700° C showing adequate sensitivity for sensor purposes. Times for the transient resistance change in the sample where used to estimate the oxygen diffusion coefficient in the ceramic. The diffusivities obtained are 4·10^–11–1·10^–12 cm²/s in the 435°–320° C range, with an activation energy of 27 kcal/mole.     

Preparation and electrical properties of Bi<Subscript>3.25</Subscript>Pr<Subscript>0.75</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript> ferroelectric thin films

Bi_3.25Pr_0.75Ti₃O₁₂ (BPT) ferroelectric thin films have been prepared by chemical solution deposition on platinized Si substrates. Well-crystallized BPT films can be achieved by 600 °C rapid thermal annealing. The film surface is smooth and crack-free, composed of uniform spherical grains around 90–100 nm in diameter. The electrical properties of Pt/BPT/Pt thin film capacitors were characterized by hysteresis and impedance measurements. The remanent polarization of 700 °C annealed BPT films is around 20 C/cm² at 120-kV/cm stimulus field. The dielectric constant is around 380 at 10 kHz, 100-mV amplitude. The remanent polarization of BPT film showed a slight reduction, 10% of its original value, after 2.8×10⁹ cycles, while a 30% reduction of non-volatile polarization was observed. PACS 81.15.-z; 77.55.+f; 77.22.Gm     

Doping properties of microcrystalline silicon prepared by mercury sensitized photochemical vapor deposition

Conductivity of photo-CVD microcrystalline silicon (c-Si:H) in wide range of dopant gas concentration (10^–53/SiH₄, B₂H₆/SiH₄<10^–2) is investigated. As compared with a-Si:H, the conductivity of the film is improved more than two orders of magnitude by microcrystallization for a wide range of dopant concentration at a deposition temperature of as low as 150°C. This indicates the suitability of photo-CVD for low temperature processing. A conductivity minimum is found at a doping ratio of about B₂H₆/SiH₄=1×10^–5.     

Determination of the strain potential constant by means of the p-InSb photoconductivity spectra under uniaxial compression

The influence of uniaxial pressure (0 < P < 2600 kg/cm2) on the intrinsic photoconductivity (PC) spectrum of p-InSb at 93 and 15°K is investigated. At 77°K the carrier concentration and mobility in the specimens were, respectively, (1.4–3.2)·10¹⁴ cm^–3 and 7000 cm²/V. sec. It is established that the maximum in the PC(E_m) spectra under compression is shifted towards higher energies. In the low-compression range E_m/P=5·10^–6eV·cm²/kg, while E_m/P=1·10^–6eV·cm²/kg for P > 1000 kg/cm². It is shown that the shift of the maximum of the intrinsic PC spectra with pressure is due to the growC;th in the forbidden bandwidth (E_g), and the change in parameters characterizing carrier diffusion in the specimen bulk (the diffusion coefficient, lifetime, surface recombination velocity) plays no part. The change in E_m/P with pressure is explained by the influence of valence band splitting. The deformation potential constants of the valence band |b|=(1.7±0.3) eV and |d|=(4.4±0.8)eV are calculated on the basis of a comparison between experimentally obtained data and theoretical results.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 159–162, February, 1976.     

Structural and optical properties of ZnO film by plasma-assisted MOCVD

High quality ZnO film was deposited by plasma-assisted metal-organic chemical vapor deposition (MOCVD). We observed a dominant peak at 34.6° due to (0 0 2) ZnO, which indicated that the growth of ZnO film was strongly C-oriented. The full-width at half-maximum (FWHM) of the -rocking curve was 0.56° indicating relatively small mosaicity. Photoluminescence (PL) measurement was performed at both room temperature and low temperature. Ultraviolet (UV) emission at 3.30 eV was found with high intensity at room temperature while the deep level transition was weakly observed at 2.513 eV. The ratio of the intensity of UV emission to that of deep level emission was as high as 193, which implied high quality of ZnO film. From PL spectrum at 10 K, we observed A-exciton emission at 3.377 eV and D°X bound exciton transition at 3.370 eV. The donor–acceptor transition and LO phonon replicas were observed at 3.333 and 3.241 eV respectively. Raman scattering was performed in back scattering at room temperature. The E₂, A_1(LO) and A_1(TO) mode was seen at 437.6, 575.8 and 380 cm^–1 respectively. In comparison with Raman spectrum of ZnO powder, we found that ZnO film was nearly free of strain, which indicated high crystal quality.     

Fast proton conductivity of polycrystalline titanoniobates

The proton conductivity of three layer-type compounds was studied: H₃OTi₂NbO₇. H₂O, HTiNbO₅ and HTiTaO₅. Measurements were made between 20 °C and 90°C on pellets pressed from crystalline powders and soaked with pure water. The hydrated compound had the highest conductivity, (20°C)-6.3–6.9·10^–4 (cm)^–1. Acid ions from the exchange process were quite firmly retained in its layer structure and contributed significantly to the measured conductivity. Consistent results were obtained after prolonged washing with water.Dedicated to Professor Harry Thomas on the occasion of his 60th birthday     

Highly (100)-oriented Eu-doped PZT thin films on sol-gel derived (100)-textured LaNiO<Subscript>3</Subscript>/Si substrates

(100)-oriented LaNiO₃ (LNO) thin films were grown on Si substrates by a sol-gel method followed by a rapid thermal process at temperatures ranging from 650 °C to 800 °C. The films produced at 700 °C had a resistivity of 1.79 mcm and could be used as bottom electrodes in the fabrication of ferroelectric capacitors on Si. Subsequently, a sol-gel derived Eu-doped Pb(Zr_0.52,Ti_0.48)O₃ (PEZT) thin film with a thickness of 130 nm prepared on the LNO electrode was found to have a (100)-oriented texture. Possible reasons for the high degree of (100) orientation in PEZT thin films are given. Good ferroelectric performance was obtained for Au/PEZT/LNO capacitors. The remnant polarization (2P_r) was found to be 22 C/cm² at a coercive electric field (E_c) of 134 kV/cm. After 10¹¹ polarization reversals, P_r decreased by only 15%. PACS 68.37.Yz; 68.37.Hk     

Electrical and optical properties of electron-irradiated ZnGeP2

Conclusions and summary The following conclusions are drawn from the reported study:The electrophysical properties of ZnGeP₂ crystals and their optical transparency in the range hG are attributable to the presence of a density-dominant (10¹⁷–10¹⁹ cm^–3) deep [E_v+(0.5–0.6) eV] growth defect associated predominantly with Zn vacancy clusters.Irradiation by high-energy electrons induces a shift of the Fermi level in the direction of E_G/2 and increases the resistivity of ZnGeP₂ to values of approximately 10¹² ·cm at 300 K. Irradiation with high-energy electrons is an effective technique for the optical bleaching of p-ZnGeP₂. The reversible modification of the optical absorption spectra of p-ZnGeP₂ in connection with irradiation and subsequent annealing indicates that the absorption step in the vicinity of h 0.6 eV is not attributable to light absorption by germanium inclusions, but to optical transition from the valence band to the growth-defect level E_v+(0.5–0.6) eV.Enhancement of the optical transmissivity of p-ZnGeP₂ in the range hG can be achieved in two wayss 1) as the result of a decrease in the density of centers with the level E_v+0.6 eV by variation of the growth conditions or subsequent annealing; 2) by shifting the Fermi level above the energy position E_v+0.6 eV through the irradiation-induced injection of compensating donor centers.The injection of radiation defects is an effective technique for controlling the electrical and optical parameters of the compound ZnGeP₂.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 122–130, August, 1986.     

The limit of stability of proton-rich thallium isotopes: a search for the decay of177Tl

The fusion reaction⁷⁴Se+¹⁰⁶Cd¹⁸⁰Pb^* at a compound nucleus excitation energy E_x 40 MeV, has been used in a search for the decay of the unknown nucleus¹⁷⁷Tl. Evaporation residues were velocity and mass analysed prior to implantation into a position sensitive silicon surface barrier detector. No evidence was discovered for the proton or alpha-decay of¹⁷⁷Tl for a cross-section > 10 _– ⁵⁺¹⁰ nb. This indicates either that¹⁷⁷Tl decays too rapidly (t_1/2 < 1=">s) by proton emission for the decay to be detected, or that¹⁷⁷Tl is produced with a cross-section less than the limit established in the present experiment. The following nuclear decay half-lives were measured with improved accuracy;¹⁷⁷Hg (t_1/2 = 130±5 ms),¹⁷⁸Hg (t_1/2=250±25 ms) and¹⁷⁷Au (t_1/2=1180±70 ms). The experiment also provided the first direct confirmation of the correct mass assignment of the alpha-decay, E=6.26 MeV, to the decay of¹⁷⁶Au. Two additional halflife measurements of proton-rich Osmium isotopes are also presented from a previous similar experiment;¹⁶⁵Os (t_1/2=73±8 ms) and¹⁶⁶Os (t_1/2 = 194±17 ms).     

Amorphous semiconducting AsSeI

It is shown on the basis of differential thermal analysis (DTA) of AsSeI samples that a reliable technique ensuring reproducible preparation of vitreous AsSeI has been found. The values of the softening and melting points are 50 °C and 220 °C, respectively.Transmittance study has been done on glasses of general compositionxAs₂Se₃+(1–x). AsSeI (forx=1.0; 0.8; 0.4; 0.0). Samples in the form of slabs of different thickness (d=0.2; 0.5; 1.0; 2.0 mm) were used to determine the wavelength dependence of the absorption coefficientK. On the basis of the results of the quoted measurements performed on thin As₂Se₃ layers in the high absorption region, the optical gap width of vitreous semiconducting AsSeI has been extrapolated, using certain simplified conceptions mentioned in the paper. The value ofE _g at 293 °K and its temperature dependence coefficient=(E _g/T)_p for AsSeI were found to be 1.91 eV and –6.7×10^–4eV/grad, respectively.     

Experimental investigation of the lattice parameter and length change near the melting point of gallium in search for premelting effects

The lattice parameter of nearly perfect gallium crystals was measured by x-ray diffraction on (440), (308) and (046) planes between 10°C and 10^–4°C close to the melting point. The thermal expansion coefficients in the three main crystallographic directions are 1.33, 3.19 and 1.62 10^–5 1/°C without anomalies. The length change was measured between 10°C and about 5 mK below the melting point in (100), (010), and (001) direction. The thermal expansion coefficients in these directions are 1.12, 3.38, and 1.85 10^–5 1/°C without anomalies. The change of the vacancy concentration between 283 K and the melting point can be estimated to 4 10^–5, the vacancy formation energy to about 0.23 eV. Premelting effects could not be detected.     

Electrical breakdown of dysprosium oxide films

The principal laws governing the electrical breakdown of dysprosium oxide films in silicon metal — insulator — semiconductor structures are investigated. The dependence of the breakdown field E_br on the rise rate of the voltage on the structure K_v, the temperature, the material and area of the electrode, and the humidity of the environment is studied. The dependence of the time delay of breakdown on the amplitude of a rectangular voltage pulse is investigated. It is established that the breakdown field increases linearly with log K_v for all insulator thicknesses, and the saturation of E_br is observed at K_v>10⁵ V/sec. It is found that E_br does not depend on the electrode material and decreases as the area of the electrode or the temperature is increased. The maximum breakdown field is determined: E _br ^max =14 MV/cm. The mechanism of the precursory stage of breakdown, i.e., the period of transient buildup of critical charge in the insulator, is discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 95–101, August, 1995.     

Thermodynamics and phase stabilities of the ternary system Li-In-Sb

Electrochemical investigations of the phase equilibria of the ternary system Li-In-Sb show the existence of two new ternary phases, Li₃InSb₂ and nominally Li₆InSb₃ which has a wide range of stoichiometry along the quasi-binary cut InSb-Li₃Sb. Both compounds are stable in equilibrium with elemental indium and antimony. The lithium activities are limited to ranges from 6.6×10^–8 to 3.6×10^–7 and 9.3×10^–8 to 1.1 ×10^–5, respectively, at 400 °C. The standard Gibbs energies of formation of Li₃InSb₂ and Li₆InSb₃ are –296.2 and –568.8 kJ/mol, respectively, at 400 °C and ideal stoichiometry. The activity ranges of Li, In and Sb are given for the stability of all phases of the ternary system.On leave from Institut für Physikalische und Theoretische Chemie, Technische Universität Graz, Austria