Оптические сечения поглощения и силы осцилляторов двойного донора магния в кремнии

The optical properties of magnesium impurity in silicon, whose atoms at interstitial positions in the lattice are deep double donors with an ionization energy of 107.56 meV in the neutral state, were studied. For optical transitions from the ground state of a neutral center to the excited levels 2p0 and 2p, the absorption cross sections and oscillator strengths were determined. These parameters were calculated from the impurity absorption spectra that were measured at T  K in samples with different magnesium concentrations. The deep donor content in the samples was determined using Hall effect measurements in the temperature range 78–300 K. The obtained characteristics of intracenter transitions in magnesium were compared with the corresponding literature data for shallow Group V donors in silicon, which are substitutional impurities. It was found that the optical characteristics of the investigated transitions in magnesium are consistent with the dependences of the corresponding parameters on the ionization energy for shallow donors, extrapolated to the region of larger electron binding energies.

Влияние одноосной деформации в направлении [110] на релаксацию состояний мелких доноров мышьяка в германии

Analysis of acoustical phonon assisted relaxation rates of arsenic donor states has been carried out in depends on uniaxial compressive stress of crystal along [110] direction under low temperature (< 10 K). As shown, under optical excitation the inversion population of donor energy levels is formed that depends on deformation of crystal. This give grounds to suppose that stimulated emission on arsenic shallow donor intracenter transitions in THz range is possible under optical excitation. As shown, uniaxial stress along [110] direction can result to switch laser transition and stimulated emission frequency

ANALYSIS OF THE SPECTRAL DEPENDENCES THE TRANSMISSION COEFFICIENT IN A BISMUTH SILICATE CRYSTAL AT HARMONIC MODULATION OF EXCESS RADIATION UNDER WAVE LENGTH

It was found that the analysis of harmonic components determining the time dependence the transmission coefficient of a bismuth silicate crystal during sinusoidal modulation of the probe radiation over the wavelength makes it possible to determine the spectral position of the maxima for intracenter transitions in defective centers contributing to impurity optical absorption. It was found that the analysis of harmonic components, which determine the time dependence transmission coefficientof an aluminum-doped bismuth titanate crystal with sinusoidal modulation of probe radiation over a wavelength, makes it possible to determine the spectral position of the maxima for intracenter transitions in defective centers that contribute to impurity optical absorption.

Оптические свойства нанокристаллов CdS, легированных цинком и медью

Cadmium-sulfide nanocrystals are produced by the colloidal method. Doping with zinc and copper is conducted during nanocrystal growth. The optical absorption and photoluminescence spectra are studied. The maximum concentration of the optically active copper impurity is determined from a shift of the fundamental absorption edge to lower energies. It is shown that the long-wavelength luminescence of CdS and CdS:Zn nanocrystals is defined by optical transitions at donor–acceptor pairs. In CdS:Cu nanocrystals, optical absorption and photoluminescence in the visible spectral region are defined by recombination transitions involving the ground state of $${\text{Cu}}_{{{\text{Zn}}}}^{{2 + }}$$ ions. The infrared absorption and photoluminescence of CdS:Cu quantum dots are defined by intracenter transitions within $${\text{Cu}}_{{{\text{Zn}}}}^{{2 + }}$$ ions.

Низкотемпературная люминесценция и термостимулированная люминесценция монокристаллов BeO : Mg

Luminescence and thermally stimulated luminescence (TL) of BeO: Mg crystals are studied at T = 6–380 K. The TL glow curves and the spectra of luminescence (1.2–6.5 eV), luminescence excitation, and reflection (3.7–20 eV) are obtained. It is found that the introduction of an isovalent magnesium impurity into BeO leads to the appearance of three new broad luminescence bands at 6.2–6.3, 4.3–4.4, and 1.9–2.6 eV. The first two are attributed to the radiative annihilation of a relaxed near-impurity (Mg) exciton, the excited state of which is formed as a result of energy transfer by free excitons. The impurity VUV and UV bands are compared with those for the intrinsic luminescence of BeO caused by the radiative annihilation of self-trapped excitons (STE) of two kinds: the band at 6.2–6.3 eV of BeO: Mg is compared with the band at 6.7 eV (STE_1) of BeO, and the band at 4.3–4.4 eV is compared with the band at 4.9 eV (STE^2) of BeO. In the visible region, the luminescence spectrum is due to a superposition of intracenter transitions in an impurity complex including a magnesium ion. The manifestation of X-ray-induced luminescence bands at T = 6 K in BeO: Mg indicates their excitation during band-to-band transitions and in recombination processes. The energy characteristics of the impurity states in BeO: Mg are determined; the effect of the isovalent impurity on the fluctuation rearrangement of the BeO: Mg structure in the thermal transformation region of STE_1 → STE_2 is revealed.

Матричный синтез монодисперсных сферических нанокомпозитных частиц SiO-=SUB=-2-=/SUB=-/GaN:Eu-=SUP=-3+-=/SUP=-

A nanocomposite in the form of monodisperse spherical mesoporous silica particles (mSiO_2) filled with GaN:Eu^3+ is synthesized by the template method. The method is based on the capillary impregnation of pores of mSiO_2 particles with a melt of crystal hydrates of gallium and europium (0.22 wt %) nitrates, followed by thermal decomposition and ammonia treatment. It is shown that nanocomposite particles contain hexagonal GaN:Eu^3+, are of spherical shape, monodisperse and do not coalesce with each other. The photoluminescence spectra of the mSiO_2/GaN:Eu^3+ particles show a group of lines characteristic of intracenter transitions in Eu^3+.

Solar Radiation Conversion With Mesoporous Silica Activated by Rare-Earth Ions

Intrinsic and extrinsic nature of the luminescence of pure and Eu3+ and Tb3+ rare-earth ions activated mesoporous silica has been investigated by spectroscopic methods. Increasing the Eu3+ impurity concentration from 0.01 mg to 7 mg, results in an increase of the impurity particles radiation in the luminescent mesoporous colloidal silica (LMCS) matrix by several times. With an increase in the concentration of Tb3+ from 0.01 mg to 3 mg, impurity luminescence intensity increases several times while the intrinsic luminescence intensity maximum at 400 and 460 nm is decreasing. Based on the experimental evidence, it is suggested that the energy of the own electronic matrix excitation is transferred by emitters, i.e., impurities of Eu3+ and Tb3+ ions. Also, it is assumed that the emission band at 610 nm in an LMCS—Eu3+ and emission band at 543 nm in the LMCS—Tb3+ is attributed to the intracenter transitions within the Eu3+ and Tb3+ ions.