V. Prosser

Preparation of cadmium telluride single crystals for nuclear detectors

Cadmium telluride single crystals, both undoped and doped with chlorine, bromine and iodine, were grown from tellurium melt. The electrical conductivity, Hall effect and photo-Hall effect were investigated. Acceptor levels located at 0·15 eV, 0·5 eV and 0·9 eV above the top of the valence band were found in samples of this semi-insulating material. A model is proposed which describes the compensation of cadmium vacancies and complexes by chlorine atoms. Chlorinedoped CdTe single crystals have proved suitable for preparation of the detectors of gammaradiation.

Preparation and basic physical properties of single crystals of cadmium chromium selenide CdCr2Se4

Single crystals of CdCr2Se4 were prepared by crystallization of polycrystalline material from the melt of cadmium chloride and by synthesis from anhydrous CrCl3 and CdSe. Basic optical and transport properties were measured on the crystals. The results are compared with the available literature data and a brief survey of existing interpretation is given.

The optical constants of single crystals of hexagonal selenium

The optical constants of single crystals of hexagonal selenium in the region of the intrinsic absorption edge in polarized light were investigated. The absorption edge for light polarized normal to the optical axis of the crystal is displaced towards longer wavelengths. The absorption maximum of hexagonal selenium for a wavelength of 0·6 μ is interpreted as the maximum corresponding to interaction between neighbouring chains and in connection with this the position of the absorption edge of different modifications of selenium is discussed.AbstractВ работе исследованы оптические постоянн ые монокристаллов ге ксагонального селена в области края собственного поглощ ения в поляризованно м свете. Край собствен ного поглощения для света, поляризованного пер пендикулярно оптиче ской оси кристалла, смещен в на правлении более длин ных волн. Максимум абс орбции гексагональн ого селена при 0,6 μ объясняе тся как максимум, соот ветствующий взаимод ействию между соседними цепо чками и в связи с этим о бсуждается местопол ожение края абсорбции разны х модиφикаций селена.

Reflectivity in yttrium iron garnet between 4 and 30 eV using synchrotron radiation

The optical reflectivity at 300 K in yttrium iron garnet YIG between 4 and 30 eV was measured using synchrotron radiation spectroscopy. By means of the Kramers-Kronig analysis and with the aid of the results of previous reflectivity experiments the spectra of complex permittivity ε′, ε′ and of the optical constants (n, k) were obtained in the range from 2 to 30 eV. The results are compared with those published by Galuza et al. [Fiz. Tverd. Tela15 (1973) 585 and17 (1975) 2863]. A good agreement with their YIG spectra is found. However, by virtue of the continuous synchrotron radiation source the present spectra reveal more details and cover a broader spectral range. A close analogy between YIG and non-magnetic yttrium gallium garnet spectra is observed above 6 eV.

Absorption and Faraday rotation of PrxY3−xFe5−yGayO12 films

Abstract Optical absorption and Faraday rotation spectra of epitaxial PrxY3−xFe5−yGayO12 films in the range 0.5−2.7 eV are reported. The contribution from Pr3+ to the rotation is strongly negative in the whole range and increases at lower temperatures. In the lower energy range some of the electronic transitions seen in the absorption spectra induce rotation. The Pr3+ contribution to the rotation is thought to arise from 4f-5d transitions rather than from any enhancement of Fe3+ transitions as is known to be the case for Bi3+. This conclusion bears some support from polar Kerr rotation studies. Finally, the strong in-plane magnetization in the films could be beneficial for integrated optical applications.

Sensitive method of measuring small changes in light intensities its use in measurements of high effective masses in semi-conductors from faraday rotation

A sensitive method for measuring Faraday rotation in the infrared region has been described. The limiting sensitivity is 10″ of rotation. The average effective mass of holes of a semi-conducting diamondm*= 0.88 m has been measured.

Picosecond absorption spectroscopy and its application to the study of nucleic acid components

A high performance picosecond absorption spectrometer adapted for induced absorption measurements in the UV region is described. An application of the spectrometer to the study of nucleic acids (NA) components is presented. Experimental results are given of induced absorption measurements in water solutions of NA components and in single crystals of NA bases.

Some photoelectric properties of the nucleic acid bases in thin layers

The current-voltage characteristics of dark-conductivity and photoconductivity, the lux-ampere characteristics, the spectral dependence of photoconductivity and the relative quantum efficiency of vacuum deposited layers of adenine, thymine, uracil and cytosine were investigated at room temperature. The following values of photoconductivity thresholdEth were obtained: 3·81 ±± 0·1 eV for adenine; 3·69±0·1 eV for thymine; 3·80±0·1 eV for uracil; 3·77 ± 0·1 eV for cytosine.It may be shown thatEth is most probably the threshold value for intrinsic photoconductivity of NA bases and, consequently, corresponds to the first electron conductivity levelE′c or at leastE′c>Eth. The possible energy diagram of the NA bases is evaluated.

Optical properties of some garnets in the fundamental absorption range

Abstract The optical reflectivity of the single-crystal garnets Y 3 Fe 5 O 12 , Y 3 Fe 4 GaO 12 , Ca 3 Fe 2 Ge 3 O 12 , Ca 3 Fe 2 Ge 3 O 12 , Y 3 Al 5 O 12 , Gd 3 Ga 5 O 12 and orthoferrite YFeO 3 between 5 and 30 eV has been measured using synchrotron radiation. By means of Kramers-Kronig analysis of the spectra, optical functions were obtained. An interpretation of the results based on interband transitions from the oxygen valence band to the unfilled conduction band formed by cation states is proposed. In the high-energy range the orbital promotion transitions between cation levels should be considered.