Optical phonon frequencies and damping in AlAs, GaP, GaAs, InP, InAs and InSb studied by oblique incidence infrared spectroscopy

The transverse (TO) and longitudinal (LO) optical phonons in AlAs, GaP, GaAs, InP, InAs and InSb have been measured at room temperature by infrared spectroscopy using an oblique incidence reflectance method. The spectra obtained were then fitted using a novel approach to determine the TO and LO phonon frequencies and damping. The results obtained are found to be more precise than in earlier reflectivity measurements using near-normal angles of incidence and provide information on the damping of both phonons. Apart from the GaAs LO mode, the observed damping parameters are found to be quite different from those predicted by theory. From these results the Lowndes condition governing the relative magnitudes of the TO and LO phonon line widths is found to be violated for all these zincblende semiconductors.     

A trend in the energy distributions of Ga dangling-orbital surface states on GaP,GaAs and GaSb (110)

Relaxed (110) surfaces of GaP, GaAs, and GaSb are studied by cluster calculations. Strongly localized surface states near the band gap are presented. It is shown that Ga dangling-orbital surface states can occur within the band gap as a result of a strong decrease in the anti-bonding character of surface Ga orbitals. A trend in the bond length on going from GaSb to GaP explains experimental data. Surface states associated with the group-V atoms are also described.     

Dissociation of 14N2+ ions induced by slow electrons

The cross sections and thermal rate coefficients for the dissociative recombination (DR) of the molecular nitrogen ions initially in the first four vibrational levels of the ground electronic state have been computed in the framework of the multichannel quantum defect theory. An energy range of 0.001–1 eV has been considered. The contribution of the indirect DR mechanism involving Rydberg states associated with the first excited ion core has also been investigated.     

N2O+离子A2∑+电子态的光解动力学研究

用一束波长为360.55nm的激光,通过N2O分子的(3+1)共振多光子电离(REMPI)过程制备纯净且布居完全处于X2Ⅱ(000)态的母体离子N2O+,然后用另一束波长在275-328nm范围内的可调谐激光将制备的N2O+离子激发至预解离电子态A2∑+.实验发现,由于解离碎片NO+所具有的一定的反冲速度,其TOF质谱峰明显比N2O+母体宽.通过分析NO+碎片TOF质谱峰形状,得到了解离产物的总平均平动能;通过考察随光解能量的变化,发现光解能量在32000cm-1附近约250cm-1的变化范围内,值由约8000cm-1突然减小至约1600cm-1.通过分析,在光解能量小于32000cm-1的区域,解离通道为NO+(X1∑+)+N(4S);而在光解能量大于32000cm-1的区域,另一个具有较高解离限的解离通道,NO+(X1∑+)+N(2D),开启并完全取代N(4S)通道成为解离的惟一通道.根据实验结果,对在所研究的光解能量范围内的N2O+离子A2∑+电子态预解离机理进行了探讨.     

ESR assessment of 3d7 transition metal impurity states in GaP,GaAs and InP

Photo-sensitive electron spin resonance of the 3d⁷-ions Fe⁺, Co²⁺, Ni³⁺ has been detected and analysed in GaP, GaAs and InP. For GaP : Ni³⁺, hyperfine interaction with the four nearest P³¹-ligands could be resolved.     

Vibrational Excitation of N2(B,C) and N+2(B) States in N2 and N2 – H2 Flowing Microwave Discharges

The ro‐vibrational spectra of N₂ microwave discharges have been analysed by emission spectroscopy. It is deduced the rotational and vibrational temperatures of N₂ states. The characteristic of vibrational temperature Θ₁ of the N₂ (X, v) ground state has been specifically determined.It has been found that the N₂ (C, B, v') and N⁺₂ (B, v') radiative states are directly excited by electron collisions on the N₂ (X,v) ground state at a N₂ gas pressure of 0.1 Torr (discharge tube of 5 mm I.D, microwave power 100 Watt) with a Θ₁ value near 10⁴ K. At higher gas pressure up to 5 Torr, the N₂ (C, v') states remain alone to be mainly excited by electron collisions on N₂ (X, v). It is considered the excitations of the N₂ (B, v') states by collisions of electrons and N₂ (X,v > 4) vibrational molecules on the N₂ (A) metastable states.With x < 9% H₂ into N₂, it is observed an increase of N₂, 2^nd pos intensity, resulting of an increase of high energy electrons. Inversely, the N₂, 1^st pos intensity decreased, partly following the decrease of low energy electrons (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

N2(B3IIg) Quenching by Ethanol

The reaction rate values for the molecular nitrogen B³II_g state quenching by ethanol for vibrational quantum numbers v′ = 4–12 have been evaluated from the change of N₂ first positive system spectrum at ethanol addition to a high speed, microwave produced, plasma flow. The wall influence is avoided using a 0.9 m large reaction chamber. Computed N₂(B³II_g) quenching rate values are comprised between 0.9 × 10^?10 and 1.4 × 10^?10 cm³ · s^?1, being smaller than the corresponding gaskinetics rate.     

Sputtering of AlxGa1−x As semiconductor targets by Ar+ ions with energies of 2–14 keV

Investigations of the sputtering of Al_xGa_1−x As semiconductor solid solutions by Ar⁺ ions with energies of 2–14 keV are performed. The dependence of the sputtering yield on the energy and angle of incidence of the ions are determined and the character of the surface relief formed during the sputtering is investigated. A comparison with theory shows that the best agreement between theory and experiment is achieved when the Haff-Switkowski formula is used together with Yudin’s stopping cross section. It is shown that the surface binding energies obtained differ from the atomization energies by an amount approximately equal to the amorphization energy. Zh. Tekh. Fiz. 67, 113–117 (June 1997)     

(4×2) and (2×4) reconstructions of GaAs and InP(001) surfaces

Received: 21 March 1997/Accepted: 12 August 1997     

Depth distribution of point defects in Si bombarded by high-energy N5+ and Si5+ ions

Electron spin resonance has been used to study the depth distribution of point defects in Si samples bombarded by N⁵⁺ (E=16 MeV) and Si⁵⁺ (E=26.8 MeV) ions at 175 and 300 K in the dose range (4–8)×10¹⁵ cm⁻². It was established that unlike the implantation of moderate-energy Si ions (E ∼ 100 keV), the depth distributions of planar tetravacancies in samples bombarded by ions at 300 K under these conditions have two maxima. The experimental results indicate that the tetravacancy density maximum closer to the surface is formed as a result of secondary defect formation processes. No continuous amorphous layer was observed in the bulk of any of the Si samples. This experimental observation is evidence of defect annealing which takes place when high-energy ions are implanted in Si. Fiz. Tverd. Tela (St. Petersburg) 40, 217–222 (February 1998)     

Oxidation and annealing of GaP and GaAs (111)-faces studied by AES and UPS

The annealing behaviour after argon sputtering and the first steps of oxidation of the polar GaP and GaAs (111)-faces are studied by AES and UPS. The Auger spectrum of GaP is briefly discussed. In contrast to GaAs, the GaP surfaces show a gallium accumulation after argon sputtering, but they become stoichiometric by annealing. The photoemission spectra show an additional emission due to oxygen with its maximum at about 5 eV below the valence band edge. The decrease of the emission near the valence band edge by oxidation shows the existence of surface sensitive states. Comparing the results of the two polar faces and for different surface compositions, it is concluded that these states are mainly As- and P-derived, respectively. A linear relationship is found between the UPS and Auger signal of oxygen.     

Intramolecular electron transfer in mixed-valence complexes [(NH3)5Ru-L-Ru(NH3)5]5+ (L = N2, pyz, pym, 4,4’-bipy, bpa)

The dynamics of the intramolecular electron transfer from Ru(II) to Ru(III) in binuclear mixed-valence complexes [NH₃)₅Ru -L-Ru(NH₃)₅]⁵⁺ (L = N₂, pyz, bipy, pym, bpa) is analyzed by the semiempirical CINDO + CI method. Translated from ZhurnalStruktumoi Khimii, Vol. 39, No. 4, pp. 579–590, July–August, 1998.     

Iron ions in ZSM-5 zeolite: Fe3+ in framework, Fe2+ in extra-framework positions in catalytic N2O decomposition

Fe-ZSM-5 samples containing a combination of ⁵⁷Fe³⁺ in framework (FW) and regular iron in extra-framework (EFW) sites were prepared by introducing ⁵⁷Fe in hydrothermal synthesis, then exchanging Fe²⁺ of natural isotope composition into the lattice. The stability for one part of Fe²⁺ and Fe²⁺ ? Fe³⁺ reversibility for the other part in catalytic decomposition of N₂O is demonstrated by in situ Mössbaer measurements. Formation of dinuclear Fe_FW–O–Fe_EFW pairs is not prevailing.     

The reactions N14(n, α)B11 and N14(n,t)C12 observed with a gridded ionization chamber

The cross sections for the reactions N¹⁴(n, α)B¹¹ and N¹⁴(n, t)C¹² have been measured in the neutron energy range 4.0 to 6.4 MeV and at 2.5 MeV. Mono-energetic neutrons were produced in the D(d, n) He³ reaction using a gas target. The (n, α) and (n, t) disintegrations were detected in a gridded ionization chamber filled with an argonnitrogen mixture. The response of the chamber under different operation conditions is described. The excitation functions, measured with a neutron energy resolution of 40 to 50 keV, are given for theα ₀ group from the N¹⁴(n,α)B¹¹ reaction over the entire neutron energy range and for theα ₁ group and the t₀ group from N¹⁴(n, t) C¹² for neutron energies above 4.3 and 5.6 MeV, respectively.     

Up-conversion luminescence phenomenon of Er~(3 ) ions in ErP_5O_(14) noncrystal glass

The up-conversion luminescence phenomenon was observed in ErP_5O_(14) noncrys-tal glass induced by pulsed DCM dye laser.Based on the difference between up-conversion ex-citation spectrum and absorption of ~4F_(9/2) and dependence of up-conversion fluorescence inten-sity on the exciting wavelength,it is found that the mechanism of up-conversion from ~4F_(9/2)level of ErP_5O_(14) noncrystal glass can not be ascribed to energy transfering between Er~(3 ) ions,a seguential absorption of two photons by a single ion should be responsible for these process.     

l-Resonance effects in the hot bands 3v 5 ← 2v 5, (v 4 + 2v 5) ← (v 4 + v 5) and (2v 4 + v 5) ← 2v 4 of acetylene

In the infrared spectrum of C₂H₂ around the fundamental v ₅, the hot bands starting from the levels 2v ₅, 2v ₄ and v ₄ + v ₅ have been investigated. From the analysis of about 20 different bands, 40 molecular constants describing the bending modes v ₄ and v ₅ have been derived.     

Raman scattering studies of (GaP)n/(InP)n (n = 1, 1.7, 2) short‐period superlattice structures

We report Raman scattering from (GaP)_n/(InP)_n (n = 1, 1.7, 2) short‐period superlattice (SPS) structures to study the effect of lateral composition modulation (LCM) on the behavior of optical phonons. Cross‐sectional transmission electron microscope images revealed that LCM was formed with complex pattern in the n = 1.7 and n = 2 samples grown at 490 °C. Interestingly, both the InP‐ and the GaP‐like longitudinal optical (LO) phonon energies increased systematically as the number of monolayers was increased from n = 1 to n = 2. A significant broadening of the phonon line shapes was also observed for the n = 1.7 and n = 2 samples. In contrast, for samples grown at 425 °C, both the increase of the LO phonon energies and the broadening of the phonon line shapes were observed only when n = 1.7. Our results demonstrate that the optical phonons in the (GaP)_n/(InP)_n SPS structures are significantly affected in the occurrence of LCM related to the growth temperature and the number of monolayers.Copyright © 2009 John Wiley & Sons, Ltd.