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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 583 (1990), S. 195-204 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Spectroscopic Investigations on Substituent Effects in SilylmethylsilanesThe silanes Me3-n(Me3SiCH2)nSiH (n = 1-3), (RMe2SiCH2)3SiH (R = n-Bu, n-Pr, Et, PhCH2, Ph) and Me3ElCH2SiMe2H (El = Ge, Sn) were prepared. The frequencies of the Si—H stretching vibration, the 29Si—1H coupling constants and the 29Si n.m.r. chemical shifts were measured. The ṽ(SiH) and J(29Si—1H) values in the silanes Me3-n(Me3SiCH2)nSiH depend on the number of trimethylsilymethyl groups. There is hardly an influence of the substituents R on these values in the silanes (RMe2SiCH2)3SiH. The frequencies of the Si—H stretching vibrations in the silanes Me3ElCH2SiMe2H (El = Si, Ge, Sn) show the order Si=Ge 〉 Sn. The 29Si n.m.r. chemical shifts of the Si(H) signals are approximately equal in the silanes Me3-n(Me3SiCH2)nSiH and (RMe2SiCH2)3SiH.
    Notes: Die Silane Me3-n(Me3SiCH2)nSiH (n = 1-3), (RMe2SiCH2)3SiH (R = n-Bu, n-Pr, Et, PhCH2, Ph) und Me3ElCH2SiMe2H (El = Ge, Sn) wurden dargestellt. Die Bandenlagen der Si—H-Valenzschwingungen, die 29Si—1H-Kopplungskonstanten und die 29Si-NMR-chemischen Verschiebungen wurden gemessen. Die ṽ(SiH)- und J(29Si—1H)-Werte der Silane Me3-n(Me3SiCH2)nSiH sind von der Anzahl der Trimethylsilylmethylgruppen abhängig. Die Substituenten R haben auf diese Werte in den Silanen (RMe2SiCH2)3SiH kaum einen Einfluß. Für die Frequenzen der Si—H-Valenzschwingungen in den Silanen Me3ElCH2SiMe2H (El = Si, Ge, Sn) ergibt sich die Abstufung Si=Ge 〉 Sn. Die 29Si-NMR-chemischen Verschiebungen des Si(H)-Signals der Silane Me3-n(Me3SiCH2)nSiH und (RMe2SiCH2)3 SiH sind annähernd gleich.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 3 (1994), S. 253-260 
    ISSN: 1057-9257
    Keywords: Seeded chemical vapour transport ; Titanium doping ; Electron spin resonance ; Paramagnetic impurities ; Static Jahn-Teller effect ; Dynamic Jahn-Teller effect ; Photoiuminescence ; Excitation spectra ; Photo-ionization of impurities ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Znse:Ti crystals were grown by seeded chemical vapour transport (SCVT) in a hydrogen atmosphere. In situ doping with titanium was carried out from an additional TiSe source in the quartz ampoule at 1460 K. The Good homogeneity of the Ti distribution and the presence of only a few defects have been demonstrated by etch pit and X-ray topography studies. For the frist time, Ti3+ (3d1) centres in a II-VI semiconductor compund are detected. The concentration of localized centres of Ti2+ and Ti3+ in high-resistivity material determined by EPR is about 5 × 1016 cm-3. Fe3+, Ni2+ and traces of Mn2+ are additionally observed. Below 77K an anisotropic EPR spectrum of Ti3+ (d1) is recorded, indicating both a dynamic and a static Jahn-Teller effect of the 2E(D) ground state. At lower temperatures clear evidence of the static Jahn-Teller effect is observed. The frist emission and excitation spectra of Ti impurities in II-VI compounds are presented. An emission near 3400 cm-1 is assigned to the 3T2(F) → 3A2(F) transition of Ti2+ (d2). Its excitation structures coincide with the known absorption bands to 3T1(P) and 3T1(F). A further structured luminescence band at 4700 cm-1 is related to 2T2 → 2E(D) transition of Ti3+ (d1). Ti ions form a deep donor level Ti2+/Ti3+ situated approximately 14,100 cm-1 above the valence band. This photo-ionization threshold is derived from the excitation measurements in accordance with previous photoconductivity experiments.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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