Universität Stuttgart
Permanent URI for this communityhttps://elib.uni-stuttgart.de/handle/11682/1
Browse
12 results
Search Results
Item Open Access Linear Stark and nonlinear Zeeman coupling to the ground state of effective mass acceptors in silicon(1992) Köpf, Andreas; Lassmann, KurtIt is shown by dielectric resonance absorption at 60 GHz that there is a linear coupling of the electric field to the ground state of effective mass acceptors in Si reflecting the lower Td symmetry in the central portion of the ground-state wave function. The coupling increases strongly with increasing binding energy from B to In, i.e., with decreasing Bohr radius of the acceptor. An unexpected nonlinear Zeeman splitting is observed the magnitude of which also increases from B to In. For all acceptors a central fine structure is found which correlates with the homogeneous linewidth.Item Open Access Phono-conduction spectroscopy of shallow states in semiconductors(1990) Lassmann, Kurt; Gienger, Martin; Groß, PeterPhonoconduction spectroscopy of shallow states in semiconductors by help of superconduction Al-junctions as phonon sources with high spectral resolution is a sensitive new technique with phonon frequencies well up in the Debye range. The large k-vector of the phonons involved opens new possibilities for the investigation of electron dynamics and states in semiconductors.Item Open Access Phonon spectroscopy of the low energy vibrations of interstitial oxygen in germanium(1993) Gienger, Martin; Glaser, Markus; Lassmann, KurtIn oxygen doped Ge we find by phonon spectroscopy with superconducting tunnelling junctions a series of lines between 0.18 meV and 4.08 meV which can be interpreted as due to low lying states of the interstitial oxygen (Oi) as a rigid rotator around a <111>-axis slightly perturbed by the lattice potential. The sequence of transitions can be fit assuming a binding angle of (106 ± 1)° which is much smaller than the value of (162 ± 1)° for Oi in Si. Line shifts and splittings with uniaxial stress along <100>, <110> and <111> are in qualitative agreement with this interpretation.Item Open Access Phonon spectroscopy of low energy vibrations of interstitial oxygen in germanium(1993) Lassmann, Kurt; Gienger, Martin; Glaser, MarkusWe can summarize our results as follows: Whereas the band of lowest lying mechanical states of interstitial oxygen in Si can be approximated by a two-dimensional oscillator perturbed by a central potential, the corresponding states in Ge can be well understood by a bindered rotator with a large central potential opposing a bending oscillation and with a sixfold modulation of the rotation due to the influence of the 6 neighbours to the Ge-O-Ge moleculeItem Open Access Resonant phonon scattering by calcium colloids in electron irradiated calcium fluoride(1993) Wurster, Clemens; Lassmann, Kurt; Eisenmenger, WolfgangHere we report on such an investigation of Ca-colloids produced by e- -irradiation in CaF2. We find a good correlation of the observed phonon scattering (and its variation with thermal treatment) with a resonance peak in the optical Mie scattering.Item Open Access Depopulation effects in the phonoconduction response of A+ -states in silicon and germanium(1990) Groß, Peter; Gienger, Martin; Lassmann, KurtWe show here that deviations from these assumptions are effective in the experiment and responsible in particular for the observed illumination dependence of the phonoconduction signal. The phonon spectrum of an Al - STJ at bias V = eU > 2ΔAl consists of a continuum with a sharp threshold at Ώm = V - 2ΔAl. In the differentiated spectrum Ώm becomes the most prominent bias-tunable feature, namely the quasimonochromatic line of phonon spectroscopy used for the approximate analysis of sharp phonon scattering resonances such as the OI line of Fig. 1a (which shows inversion of the center due to strong scattering).Item Open Access Linear stark coupling to the ground state of effective mass acceptors(1989) Köpf, Andreas; Ambrosy, Anton; Lassmann, KurtIt is shown by dielectric resonance absorption at 24 GHz and by ultrasonic resonance spectroscopy between 5 and 10 GHz that linear coupling of the electric field to the ground state of effective mass acceptors in Si exists and has a distinct chemical shift from B to In.Item Open Access Investigation of A+-states in Si and Ge by phonon-induced conduction under uniaxial stress(1993) Groß, Peter; Lassmann, KurtBy the analysis of the stress dependence of phonon induced conductivity (PIC) with superconducting Al-tunneling junctions as phonon generators we have now found strong evidence for a split ground state in the cases Si:Ga+, Si:Al+ and Ge:Zn+.Item Open Access Recent developments in phonoconductivity spectroscopy of shallow bound states in semiconductors(1991) Lassmann, Kurt; Gienger, Martin; Groß, PeterThe phonon emission spectrum of a superconducting Al-junction contains a sharp quasi-monochromatic lineup to the range of Debye energies tuneable by the bias. This is evident from steep phonon-induced conduction (PIC) thresholds due to excitation of carriers in semiconductors from shallow bound states to the neighbouring band. Information on phonon coupling to carriers and phonon propagation at extremely high frequencies in superconductors and semiconductors can be obtained from such experiments.Item Open Access One-phonon ionization of donors in germanium by intervalley scattering : phonon spectroscopy with superconducting aluminium junctions at Debye frequencies(1990) Gienger, Martin; Groß, Peter; Lassmann, KurtOne-phonon ionization of donors in germanium via intervalley scattering by slow TA phonons at the X point of the Brillouin zone is demonstrated by the stress dependence of phonoconductivity. Superconducting aluminum junctions are used as tunable quasimonochromatic phonon sources up to these extreme frequencies. The ionization probability is found to be increased when donor levels associated with stress-shifted higher valleys of the conduction band cross the lowest valley(s).