Electrical properties of neutron-transmutation-doped InSe

Neutron-transmutation-doping (NTD) has been used to introduce a controlled amount of tin-related shallow donors with a uniform distribution into the layered semiconductor InSe. The electrical properties of transmutation-doped (TD) InSe, between 30 and 300 K have been measured and compared with those of InSe conventionally tin-doped during growth. After annealing at 450°C, the lattice damage associated with NTD is removed and the donor centres become electrically active. For concentrations of transmutated Sn bigger than 10¹⁷ cm^-3 the free-electron concentration saturates and this is interpreted as a result of segregation determined by the Sn solubility limit in the host lattice. The Hall mobility at room temperature is higher in TD samples than in conventionally tin-doped ones for the same electron concentration.     

片状放大器热恢复研究

 给出了神光III主放大器单元4×2×3片状放大器的热恢复研究。利用集总热容模型研究了氙灯、隔板玻璃、钕玻璃片的热恢复过程,并利用三维瞬态热传输有限元模型对钕玻璃片的三维空间温度随时间的变化过程作了详细的分析。初步的研究结果表明,通过优化的冷却方案,可以在装置预定的运行周期内将激光工作介质钕玻璃片内的温度梯度和总体平均温度冷却到可以接受的水平。     

片状放大器热恢复研究

给出了神光III主放大器单元4×2×3片状放大器的热恢复研究。利用集总热容模型研究了氙灯、隔板玻璃、钕玻璃片的热恢复过程,并利用三维瞬态热传输有限元模型对钕玻璃片的三维空间温度随时间的变化过程作了详细的分析。初步的研究结果表明,通过优化的冷却方案,可以在装置预定的运行周期内将激光工作介质钕玻璃片内的温度梯度和总体平均温度冷却到可以接受的水平。     

Thermal Neutron damage in cadmium

The isochronal annealing of the damage produced by thermal neutron irradiation of cadmium at 3.6 °K has been studied for several initial doses which vary by a factor of 1000. The recovery results show a strong dependence upon initial dose. This effect, which is not seen to this extent in the fcc metals, cannot be accounted for by an irradiation annealing mechanism. In contrast to the observation of two processes involving long range defect migration for several fcc metals only one process, at high temperatures, is discernable from isochronal annealing of Cd. The presence of another process at low temperatures is clearly established by other means. Irradiation annealing effects observed during the production of damage at high defect concentrations indicate that the spontaneous annihilation volume between the defects of a new capture event and the defects from an earlier event is 80 atomic volumes. Other results suggest that damage production and recovery mechanisms may be associated with the anisotropic nature of the cadmium hexagonal lattice.     

Thermal and optical studies of an amorphous InSe9 alloy produced by mechanical alloying

In this paper we investigated thermal and optical properties of an amorphous alloy of the In–Se system. The amorphous InSe₉ alloy was produced by mechanical alloying and it was studied using Differential Scanning Calorimetry and microPhotoluminescence spectroscopy techniques, and from them several properties, such as glass transition and crystallization temperatures and energies and the optical gap energy were determined and compared to the values found in other alloys of the In–Se system. This comparison revealed some differences among our alloy produced by mechanical alloying and alloys produced by other techniques, which is a clear indication of the influence of the fabrication technique in their physical properties. The main differences occur in the activation energies associated with the glass transition and crystallization processes and also in the optical gap energy.     

Second harmonic generation in InSe

Experimental evaluation of non-linear susceptibility coefficient d₂₂ for InSe, which is responsible for second harmonic generation in this material at 1.06 and 10.6 μm, is reported and the value compared with GaSe. At the CO₂ laser frequency of oscillation, phase matching has been observed and a value of d₂₂ almost equal to d₁₅ for CdSe has been found. The InSe high transparency in the wavelength range 1.1–22 μm, the sizeable value of d₂₂ and the possibility of reaching phase matching condition in the IR range make InSe a potential device for far IR frequency conversion.     

Thermal equation of state for lattice Boltzmann gases

The Galilean invariance and the induced thermo-hydrodynamics of the lattice Boltzmann Bhatnagar--Gross--Krook model are proposed together with their rigorous theoretical background. From the viewpoint of group invariance, recovering the Galilean invariance for the isothermal lattice Boltzmann Bhatnagar--Gross--Krook equation (LBGKE) induces a new natural thermal-dynamical system, which is compatible with the elementary statistical thermodynamics.     

Self-radiation damage and recovery in Pu-doped zircon

Abstract

The effects of self-radiation damage due to alpha decay was studied as a function of cumulative decay events in synthetic zircon doped with ²³⁸Pu. The density of the Pu-doped zircon decreased exponentially with dose to a value corresponding to a density change of 14.2% at saturation. The initially crystalline material became fully X-ray amorphous at a dose of 6.7 × 10¹⁸ alpha decays/g. Isochronal annealing indicated that recovery associated with recrystallization of amorphous zircon occurs in two stages, with estimated activation energies of 5.1 ± 0.2 and 6.6 ± 0.3 eV. These results are in good agreement with behavior observed in studies of self-radiation damage over geologic time in natural zircons.     

Electronic properties of the layer semiconductor InSe

The three-dimensional band structure of InSe is calculated by the tight-binding and pseudopotential methods. The two band structures have many features in common and both agree with most optical and photoemission data. The high ionicity of this compound is reflected in the low dispersion of the energy bands and is evidenced by a calculation of the total valence charge density.     

Thermal neutron damage in CdS and CdTe

Photoluminescence and electrical resistivity changes in CdS and CdTe produced by thermal neutrons are discussed. The damage is produced principally by the neutron capture reaction ¹¹³Cd (n,y) ¹¹⁴Cd. Since the reaction product ¹¹⁴Cd is stable, complications arising from impurity introduction is minimal. The cumulative recoil nuclear recoil energy is about 143 eV, but is not the recoil energy at the time atomic displacement occurs. Thermal and fast neutrons enhance the CdS luminescence band at 7200A in the ratio of 28:1, but the resistivity changes are in the ratio of 40:1 Cd interstitial is suggested as the luminescence center. Hall measurements on n-type CdTe suggest that only Cd defects are produced for low thermal neutron doses. The acceptor introduction rate is about 1.0 to 0.6, compared to 0.098 for CdS. These are in good agreement with the values reported by R. O. Chester. The fast neutron effects in high resistivity CdS reported by Johnson indicate the need for further measurement.     

Excitons and electron-hole plasma in InSe

The spontaneous emission from either thin or thick samples of layered indirect-gap InSe semiconductor under dye laser excitation has been investigated either above or below the critical Mott density. The observed spectra consist of five bands in the near infrared region; four of them are localized in the energy range between the direct and the indirect gap and one only lies below the indirect energy gap. These bands can be associated with cooperative indirect and direct excitonic transitions and with electronhole plasma recombinations.     

Time resolved photoluminescence of Cd-doped InSe

High resolution and time resolved photoluminescence in low resistivity Cd dopedp-type InSe in the 32K–155K temperature range are reported. The photoluminescence spectra consist of a broad band that turns out to have three components with different lifetimes (less than 0.1 s, 2.1±0.1 s and 17±1 s). For a given sample, the relative contribution of the components depends on the excitation conditions. The two components with longer lifetime have an asymmetric gaussian shape and a temperature dependence of both the intensity and the decay time which suggest that they are emitted by complex centers, in which the ground state originates from the Cd related acceptor. The fast component and the weak structures in the high energy tail of the broad band, with much shorter lifetime, are proposed to be due to distant donor-acceptor pair recombination.     

Thermal monopoles in the SU(2) gauge theory on a lattice

Color-magnetic thermal monopoles in SU(2) lattice gluodynamics with improved Simanzik action were studied. The density of the monopoles, the monopole chemical potential, the cluster susceptibility, and the cluster magnetization were studied. These results were compared with results that were reported elsewhere.     

Electron paramagnetic resonance in neutron-transmutation-doped semiconductors with a changed isotopic composition

Potential applications of electron paramagnetic resonance (EPR) for investigating and controlling the process of neutron transmutation doping (NTD) of semiconducting germanium, silicon, and silicon carbide are discussed. It is shown that EPR enables one to control the process of annealing of radiation-induced defects in semiconductors subject to neutron irradiation and to detect the shallow donors restored in the process of annealing of donor-compensating defects by observing EPR signals from these donors. EPR can be used to separately detect isolated donors and clusters of two, three, and more exchange-bound donor atoms and thereby determine the degree of nonuniformity of the impurity distribution over the crystal. Neutron transmutation doping is demonstrated to produce a fairly uniform arsenic-donor distribution in a germanium crystal. It is argued that semiconductors enriched in the selected isotopes should be used for NTD. The results of an investigation of phosphorus donors in silicon carbide are presented.     

Anomalous thermal expansion of InSe layered semiconductors in the low-temperature region

The temperature dependence of the linear thermal expansion coefficient (TEC) of an InSe single crystal in the (001) plane is measured in the temperature range 7–50 K. A peak in the thermal expansion is detected near T = 10 K, after which the sample shrinks upon heating. The effect of an external magnetic field of up to 6 T, which is parallel to the (001) plane, on the TEC is investigated. The observed partial suppression of the peak and crystal compression by the field indicates the relation of these anomalies to possible electron ordering in InSe layers.