The relaxation time study by Shubnikov-De Haas effect in Pb0.82Sn0.18 Te narrow band-gap semiconductors

The nature of broadening of the Landau levels in Pb_0.82Sn_0.18Te on the basis of recent experimental data is discussed. One needs to take into account the dependence of the monotonic part of magnetoresistance on the magnetic field H to determine the Dingle temperature on the Shubnikov-de Haas data. The Dingle temperature in solid solutions of Pb_0.82Sn_0.18Te is large (T_D=2.2?24.8 K) and depends on H. The T_D(H) dependence is explained of the transition to quantum limit. In this case the relaxation time _D=?(πkT_D)^?1 is increased with rising of the magnetic field, which is in accordance with the theory of Abrikosov. The _D/₀ dependence on carriers concentration can explain scattering on short range potential supposing the total scattering cross-section to be $\text{S}{}_{\mathrm{T}}\text{～?}{}^{\mathrm{<mtext>?1</mtext><mtext>2</mtext>}}$. It was shown that the presence of random fluctuations of crystal potential in the solid solution is the most possible reason of broadening of the quantum levels. The experiment supports the dependence T_D ～ √n obtaining theoretically. cally.     

g-Factors of high-spin isomers in 194Hg and 196Hg

The g-factors of the 10⁺ isomeric states in ¹⁹⁴Hg and ¹⁹⁶Hg have been measured using the in beam IPAD method. The results $\text{g(}{}^{194}\text{Hg}\text{) = ?0.24(4)}$ and $\text{g(}{}^{196}\text{Hg}\text{) = ?0.18(9)}$ are in agreement with the value expected for an ($\text{i}{}_1\text{3}\text{2}$^?2) neutron satructure and clearly contradict the previous assignment as ($\text{h}{}_{\mathrm{<mtext>1</mtext><mtext>1</mtext><mtext>2</mtext>}}{}^{\mathrm{?2}}$) proton configurations. Cranking model calculations show that the neutron excitation energies in the rotating frame agree satisfactorily with the experimental energies and that the proton excitations are expected ≈2 MeV above the experimental yrast line     

Sputter cleaning and dry oxidation of CdTe,HgTe, and Hg0.8Cd0.2Te surfaces

The analyses of CdTe, HgTe, and Hg_0.8Cd_0.2Te surfaces by XPS and LEED after Ar⁺ sputtering and after the subsequent onset of a dry oxidation are described, and a quantitative evaluation of the XPS spectra is attempted. The results are: Ar⁺ sputtering yields a perfect unreconstructed CdTe surface of stoichiometric composition, whereas the composition of sputtered HgTe and Hg_0.8Cd_0.2Te surfaces generally deviates from the stoichiometry of the respective compound. This deviation is a function of the energy of the Ar ions (1 to 15 keV) and is characterized by an increasing deficit in Hg as the ion energy is raised. The Hg deficit of sputtered Hg_0.8Cd_0.2Te surfaces is substitutionally compensated by an equivalent increase in Cd, and due to this substitution the resulting surfaces are sufficiently ordered to display a distinct LEED pattern. The oxidation of sputtered CdTe, HgTe, and Hg_0.8Cd_0.2Te surfaces in an O₂ atmosphere is an extremely slow process. Therefore, the surfaces to be oxidized were additionally exposed to UV radiation (low pressure mercury lamp), and due to UV generated ozone as an oxidizing agent ultrathin native oxide layers of up to 15 Å thickness were readily obtained. The predominant constituents of these native oxide layers on Hg_0.8Cd_0.2Te are concluded to be CdTeO₃ and TeO₂.     

Quadrupole moment of the 5−2, 134 keV state in 197Hg

The quadrupole interaction for the $\text{5}{}^{\mathrm{?}}\text{2}\text{, 134}\text{keV}$ state of ¹⁹⁷Hg in solid Hg was observed by the e^?-γ time differential perturbed angular correlation method. The quadrupole coupling constant ν_Q=126 (2) MHz is derived. By comparison with experimental quadrupole coupling constants for ¹⁹⁹Hg in Hg and HgCl₂ as well as for ²⁰¹Hg in HgCl₂ the quadrupole moment of the $\text{5}{}^{\mathrm{?}}\text{2}\text{, 134}\text{keV}$ state in ¹⁹⁷Hg is related to that of the ²⁰¹Hg ground state, which is known. The value $\text{Q(}{}^{197}\text{Hg}\text{,}\text{5}{}^{\mathrm{?}}\text{2}\text{, 134}\text{keV}\text{)=0.47(6)}\text{b}$ is deduced. This value is not in agreement with the assumption of a $\text{f}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ shell-model configuration for the 134 keV state. It is consistent with an interpretation of the $\text{5}{}^{\mathrm{?}}\text{2}$ level in terms of the core coupling model of de Shalit.     

Determination of the fermi surface of monoclinic SrAs3 by Shubnikov dehaas effect

The electronic properties of single crystals of monoclinic SrAs₃ have been studied by investigating the temperature dependence of electrical conductivity, Hall effect and Shubnikov de Haas (SdH) oscillations. At 4.2 K, SrAs₃ is predominantly p-conducting with a typical hole concentration of 6 × 10¹⁷cm^-3. The Hall coefficient changes its sign near 80 K. The angular dependence of the SdH oscillations was used to map out the shape of the Fermi-surface of holes. Two asymmetric, quasi-ellipsoidal Fermi-bodies are located in the first Brillouin zone. The cyclotron effective masses $\text{m}{}^1$ for two crystallographic directions were calculated from the temperature dependence of the amplitude of the oscillations: $\text{m}{}^1\text{(B6a)=(0.70± 0.002)m}{}_0$and $\text{m}{}^1\text{(B6c}{}^1\text{)=(0.095±0.003)m}{}_0$, respectively. There are indications for a third Fermi-surface which is attributed to electrons.     

Hole mobility in p-type HgTe

Experimental data concerning the electrical conduction and Hall coefficient in HgTe samples with acceptor states have been collected and analysed. In the analysis three ranges of acceptor concentration have been distinguished: a low concentration range up to about 5 × 10¹⁵ cm^?3 (pure samples), a high concentration range from 10¹⁶ to 10¹⁸ cm^?3 (p-like samples), and an extremely high concentration range above 10¹⁸ cm^?3 (p-type samples). In pure HgTe samples the holes are in the valence band, in p-like samples the “holes” are in the impurity band, and in p-type HgTe samples the holes are in a strong mixing impurity-valence band. The mobility of holes in the valence band is of the order of $\text{10}{}^5\text{cm}{}^2\text{Vs}$. The mobility of “holes” in the impurity band decreases with increasing impurity concentration from about $\text{5 × 10}{}^3\text{cm}{}^2\text{Vs}$ to $\text{125}\text{cm}{}^2\text{Vs}$. The mobility of holes in p-type HgTe samples is independent of the acceptor concentration and is equal to $\text{125}\text{cm}{}^2\text{Vs}$.     

Some thermomagnetic transport effects of Cd3P2

In this paper for the first time measurements are presented of the transverse Nernst effect, the Righi-Leduc effect and the Maggi-Righi-Leduc effect in cadmium phosphide. The measurements were performed on unoriented Cd₃P₂ single crystals, with electron concentrations in the range 0.05–1.7 × 10²⁴m^?, at 110 and 300 K in magnetic fields up to 1.8 $\text{Wb}\text{m}{}^2$. We also measured the room temperature dependence of the zero-field Seebeck coefficient on electron concentration of a large number of undoped and Cu-doped samples. A reversal of sign of the transverse Nernst effect was observed at an electron concentration of about 1.2?1.5 × 10²⁴ m^?3. This reversal of sign and the zero-field Seebeck coefficient vs electron concentration for undoped material can be quantitatively described by a Kane-type conduction band with ?_g = 0.50 eV, m¹_e = 0.040 m_o and a scattering parameter r = ?1. (Optical phonon scattering, if interpreted in a single mode.) This strongly confirms the results of Radautsan et al. that Cd₃P₂ has a non-parabolic Kane-type conduction band. The Righi-Leduc and Maggi-Righi-Leduc effect measurements at 110 K on samples with high electron concentrations, yielded Lorenz numbers only half their theoretical values, indicating that the electron scattering contains an inelastic contribution.     

Softening of acoustic and optical modes in ferroelastic phase in Hg2Br2

The softening of an acoustic and an optical phonons in Hg₂Br₂ has been investigated by means of the light scattering technique.It has been observed that the cube of the frequency of the soft optical phonon varies proportionally with the temperature below T_c.An expression for the relation of the elastic constant C₆₆ to the temperature has been derived from the phenomenological thermodynamic potential function. The observed temperature dependence of the elastic constant and the optical phonon frequency is described when we assume that the order parameter Q varies as $\text{Q ∝ [T ? T}{}_0\text{]}{}^{\mathrm{<mtext>1</mtext><mtext>6</mtext>}}$.     

A piezomodulation study of the absorption edge and Mn++ internal transition in Cd1−xMnxTe,a prototype of diluted magnetic semiconductors

We report the first piezomodulation spectrum of Cd_1?xMn_xTe. Signatures of the exciton transition and the internal transition of Mn⁺⁺ are identified. The opposite signs of these signatures are attributed to the positive pressure coefficient of the direct interband transition as contrasted to a negative pressure coefficient for the ${}^6\text{A}{}_1\text{→}{}^4\text{T}{}_1$ transition causing the Mn⁺⁺ feature.     

Longitudinal magnetoresistance in zero-gap CdxHg1−xTe at low temperatures

The longitudinal magnetoresistance Δ?₆(H)/?₀ is studied experimentally in gapless solid solutions Cd_xHg_1?xTe (0 < x < 0.15) for temperatures 1.3–15 K and the electron concentrations n ～ 10¹⁵ cm^?3. The temperature and the magnetic field dependences of the observed negative longitudinal magnetoresistance are explained by the resonant nature of electron scattering by an acceptor level. The quantitative analysis of the $\text{Δ?6(H)}\text{?}{}_0$ field dependence for weak magnetic fields under strong carrier degeneracy makes it possible to evaluate parameters of the acceptor level involved.     

Model calculation of the electronic structure and spectroscopy of Hg2

Energy curves and transition moments of the excited valence states of Hg₂ were obtained in a model calculation based on calculated Mg₂ energy levels and the assumption that the asymptotic spin-orbit matrix elements for the Hg atom are applicable to the molecular states. The spin-orbit and orbital-rotational interaction of the excited states of Hg₂ is analyzed in both a Hund's case (c) and (a) representation. The intermediate (a) → (c) transition moments are obtained as a function of the internuclear distance. The effect of the orbital-rotational interaction which introduces Hund's case (b) and (e) couplings is found to be small for transitions among excited states under the conditions normally encountered for populating excimer states.Using the energy level positions and transition moments, the observed spectra and predicted spectra are compared for both radiative transitions including the ground state and among the excited states. The lifetime of the $\text{1}{}_{\mathrm{u}}\text{(}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{)}$ excimer state is calculated to be 1.4 μsec with the 335 nm band assigned to the $\text{1}{}_{\mathrm{u}}\text{→ X}{}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ transition. The 485 nm bands cannot be assigned to any Hg₂ transitions. Strong bound-continuum absorptions are predicted for the 485 nm bands. On the other hand, the 335 nm emission is predicted to be absorbed by bound-bound transitions only.     

Calculation of the carrier concentration dependence of the Auger lifetime in degenerate n-type (Hg,Cd)Te

The Auger 1 lifetime expression for degenerate n-type (Hg_1?xCd_x)Te has been derived by replacing the Fermi-Dirac distribution functions for the pair of Auger collision electrons with step functions. The lifetime is calculated as a function of carrier concentration, _n0 for several values of energy gap and temperature using a non-parabolic band structure. We find that for strong degeneracy, the lifetime, τ_AlsuD varies as n₀^?γ where 0.7 ?γ? 1 and that γ is dependent upon the energy gap. The relatively slow dependence of τ_Al^D upon n₀, compared to the non-degenerate case () is due to the dependence of τ_Al on the threshold energy which for the degenerate case is a linear function of the Fermi energy, hence, a function of n₀.     

Accurate determination of the 17O16O + n coupling constant and spectroscopic factor

We have measured ¹⁶O¹⁷O elastic cross sections at 22 MeV between 65°–140° to ± 1 %. The observed oscillatory interference between Coulomb scattering and the neutron transfer process is analyzed using exact finite-range DWBA. A model-independent value of $\text{C}\text{?}{}^2\text{= 0.82 ± 0.07}$ is obtained for the coupling constant of the 1d_{$\text{5}\text{2}$} neutron in ¹⁷O. We also present an analysis of data on magnetic electron scattering from ¹⁷O, which yields precise information on the magnitude and the radial shape of the $\text{1}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ neutron bound-state wave function. With this we relate the coupling constant to the spectroscopic factor and find S = 1.04 ± 0.11. We show that the magnetic electron scattering data alone yield S = 1.04 ± 0.10. Combining these results with earlier work we recommend $\text{C}\text{?}{}^2\text{= 0.79 ± 0.04}$ and S = 1.03 ± 0.07 as best values. This spectroscopic strength corresponds to (91 ± 7) % of the full single-particle value.     

Sudden change of quadrupole moment between the first 52− states of 197Hg and 199Hg

Low-temperature time differential perturbed angular correlation experiments with the 164 keV-134 keV cascade of ^197mHg in a zinc matrix give evidence that the hitherto accepted value of the quadrupole moment of the first $\text{5}\text{2}{}^{\mathrm{?}}$ state of ¹⁹⁷Hg is erroneous. A new value is derived from a time differential perturbed angular correlation experiment with the 374 keV?158 keV cascade of ^199mHg implanted into a Be single crystal and comparison with an analogous experiment for ^197mHg. Taking $\text{Q(}\text{5}\text{2}{}^{\mathrm{?}}\text{,}{}^{199}\text{Hg) = +0.95(7)}\text{b}$ we derive $\text{|Q(}\text{5}\text{2}{}^{\mathrm{?}}\text{,}{}^{197}\text{Hg)¦= 0.081(6)}\text{b}$. This change of quadrupole moment is discussed in the framework of the shell model.     

Spin measurements and reaction mechanism in the inelastic scattering of 18O on 12C

The alpha-decay of states in ¹⁸O have been studied in the inelastic scattering reaction ${}^{12}\text{C}\text{(}{}^{18}\text{O}\text{,}{}^{18}\text{O}{}^1\text{→}{}^{14}\text{C}\text{-α)}$ at 82 MeV. The double differential cross sections have been analysed with a strong absorption model. A systematic dependence of emission angle on spin is observed, allowing the determination of the transferred angular momentum.     

Ultraviolet absorption spectra of Zn2 and Cd2 in solid argon and krypton at 10 K

Zinc and cadmium atoms have been condensed with argon and krypton at 10 K. The most intense absorption is due to the ${}^1\text{P}{}_1\text{←}{}^1\text{S}{}_0$ atomic transition, and a weak band is due to the ${}^3\text{P}{}_1\text{←}{}^1\text{S}{}_0$ atomic absorption. Structured absorptions at 252 and 254 nm in solid argon and krypton with vibrational spacings of 140-120 cm^?1 are due to the ${}^1\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{←}{}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ transition of Zn₂. Similar 273 and 277 nm absorptions with 110-90 cm^?1 vibrational spacings are due to Cd₂ in solid argon and krypton, respectively.     

Simple Z01 model

A model for isoscalar KN scattering near the K¹N threshold is constructed, and solved analytically in the approximation of retaining only pion exchange terms. Basic features of phenomenological phase shits are reproduced, including a wide $\text{J}{}^{\mathrm{P}}\text{=}\text{1}\text{2}{}^{\mathrm{+}}$ exotic resonance, Z₀¹(1800).     

Analysis of the Ã1A″ ← X̃1A′ electronic transition in thiocarbonyl chlorofluoride

The visible absorption spectrum of thiocarbonyl chlorofluoride, ClFCS, in the region 5000 to 3000 Å has been observed under conditions of high resolution in the vapor phase and has been assigned to the $\text{A}\text{?}{}^1\text{A″(nπ}{}^1\text{) ←}\text{X}\text{?}{}^1\text{A′}$ and $\text{a}\text{?}{}^8\text{A″(n, π}{}^1\text{) ←}\text{X}\text{?}{}^1\text{A′}$ electronic transitions. All six fundamental modes have been assigned for both the upper and lower singlet electronic states. From the observed splittings of the even-odd quanta of ν₆′ in the spectrum the barrier to inversion in the $\text{A}\text{?}{}^1\text{A″}$ state has been evaluated to be 1556.0 ± 45 cm^?1.     

Lifetime of electronic states of CO2+

The radiative lifetimes of the $\text{A}\text{?}{}^2\text{Π}{}_{\mathrm{u}}$ and $\text{B}\text{?}{}^2\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ states of CO₂⁺ were measured by means of the delayed coincidence method. Excitation was performed by a pulsed electron beam incident on CO₂. The results of these measurements are 115 ± 5 nsec for the $\text{A}\text{?}{}^2\text{Π}{}_{\mathrm{u}}$ state and 126 ± 3 nsec for the $\text{B}\text{?}{}^2\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ state.     

Effects of annealing on the electrical properties of HgTe crystals

The carrier mobility of HgTe crystals at 15°C increased to as much as $\text{33,000}\text{cm}{}^2\text{V sec}$, and the transverse magnetoresistance decreased, when the crystals were annealed long enough in mercury vapor. The results are compared with our calculations of the galvanomagnetic effects for mixed scattering by phonons and charged centers, which was made for a parabolic band. It is concluded that the density of charged centers decreases with annealing, and that acoustic phonons may be the dominant scattering sources near room temperature.