TY  - JOUR
A1  - Becker, Charles R.
T1  - Impurity-induced absorption in or near the phonon gap of KI
N2  - In or near the phonon gap of KI a single weak line due to OW (OD\(^-\)) at 69.7 (69.3) cm\(^{-1}\) has been observed. A second and much stronger line at 94.1 cm\(^{-1}\) was shown not to be related to OH\(^-\), but instead is thought to be due to CO\(_3\).
Y1  - 1970
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-30757
ER  - 
TY  - JOUR
A1  - Becker, Charles R.
T1  - Evidence for a quasi-phonon gap in CsCl
N2  - The observed impurity induced far-infrared absorption in CsCl : Rb\(^+\) and CsCl : K\(^+\) is compared with a calculated density of acoustic phonon states in CsCl. The absorption due to CsCl : Rb\(^+\) displays a minimum between the acoustic and optic phonon bands. A narrow line is observed in CsCl: K\(^+\) at 85.8 cm\(^{-1}\) which falls in this quasi-phonon gap.
Y1  - 1971
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-30767
ER  - 
TY  - JOUR
A1  - Becker, Charles R.
A1  - He, L.
A1  - Einfeldt, S.
A1  - Wu, Y. S.
A1  - Lérondel, G.
A1  - Heinke, H.
A1  - Oehling, S.
A1  - Bicknell-Tassius, R. N.
A1  - Landwehr, G.
T1  - Molecular beam epitaxial growth and characterization of (100) HgSe on GaAs
N2  - In this paper, we present results on the first MBE growth of HgSe. The influence of the GaAs substrate temperature as well as the Hg and Se fluxes on the growth and the electrical properties has been investigated. It has been found that the growth rate is very low at substrate temperatures above 120°C. At 120°C and at lower temperatures, the growth rate is appreciably higher. The sticking coefficient of Se seems to depend inversely on the Hg/Se flux ratio. Epitaxial growth could be maintained at 70°C with Hg/Se flux ratios between lOO and ISO, and at 160°C between 280 and 450. The electron mobilities of these HgSe epilayers at room temperature decrease from a maximum value of 8.2 x 10^3 cm2 /V' s with increasing electron concentration. The concentration was found to be between 6xlO^17 and 1.6x10^19 cm- 3 at room temperature. Rocking curves from X-ray diffraction measurements of the better epilayers have a full width at half maximum of 5S0 arc sec.
KW  - Physik
Y1  - 1993
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-50947
ER  - 
TY  - JOUR
A1  - Becker, Charles R.
A1  - He, L.
A1  - Regnet, M. M.
A1  - Kraus, M.M.
A1  - Wu, Y. S.
A1  - Landwehr, G.
A1  - Zhang, X. F.
A1  - Zhang, H.
T1  - The growth and structure of short period (001) Hg\(_{1-x}\)Cd\(_x\)Te-HgTe superlattices
N2  - Molecular beam epitaxially grown short period (001) Hg\(_{1_x}\)Cd\(_x\)Te-HgTe superlattices have been systematically investigated. Several narrow well widths were chosen, e.g., 30, 35 and 40 Å, and the barrier widths were varied between 24 and 90 Å for a particular well width. Both the well width and the total period were determined directly by means of x-ray diffraction. The well width was determined by exploiting the high reflectivity from HgTe and the low reflectivity from CdTe for the (002) Bragg reflection. Knowing the well and barrier widths we have been able to set an upper limit on the average Cd concentration of the barriers, \(\overline x_b\), by annealing several superlattices and then measuring the composition of the resulting alloy. \(\overline x_b\) was shown to decrease exponentially with decreasing barrier width. The structure of a very short period superlattice, i.e., 31.4 Å, was also investigated by transmission electron microscopy, corroborating the x-ray diffraction results.
Y1  - 1993
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-37858
ER  - 
TY  - JOUR
A1  - Becker, Charles R.
A1  - Lau, Ph.
A1  - GEICK, R.
A1  - Wagner, V.
T1  - Antiferromagnetic Resonance in NiO:Co\(^{2+}\) and NiO:Fe\(^{2+}\)
N2  - No abstract available.
Y1  - 1975
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-30772
ER  - 
TY  - JOUR
A1  - Becker, Charles R.
A1  - Martin, T. P.
T1  - Infrared absorption by Impurity-pair resonant modes in NaCl:F
N2  - New resonant-mode infrared absorption lines have been observed in NaCl with high concentrations of fluorine impurities. The quadratic concentration dependence of the strength of these lines indicates that they are due to pairs of fluorine impurities. At the resonant frequencies, the motion of some host ions appears to be as important as the motion of the impurities themselves.
KW  - Festkörperphysik
Y1  - 1972
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-37840
SN  - 1098-0121
ER  - 
TY  - JOUR
A1  - Becker, Charles R.
A1  - Nath, G.
T1  - Optical properties of LiIO\(_3\) in the far infrared
N2  - No abstract available
Y1  - 1970
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-37905
ER  - 
TY  - JOUR
A1  - Becker, Charles R.
A1  - Wu, Y. S.
A1  - Waag, A.
A1  - Kraus, M. M.
A1  - Landwehr, G.
T1  - The orientation independence of the CdTe-HgTe valence band offset as determined by x-ray photoelectron spectroscopy
N2  - No abstract available
Y1  - 1991
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-30784
ER  - 
TY  - JOUR
A1  - Becker, Charles, R.
A1  - Latussek, V.
A1  - Heinke, H.
A1  - Regnet, M. M.
A1  - Goschenhofer, F.
A1  - Einfeldt, S.
A1  - He, L.
A1  - Bangert, E.
A1  - Kraus, M. M.
A1  - Landwehr, G.
T1  - Molecular beam epitaxial growth and characterization of (001) Hg\(_{1-x}\) Cd\(_x\) Te-HgTe superlattices
N2  - The molecular beam epitaxially growth of (001) Hg\(_{1-x}\) Cd\(_z\) Te-HgTe superlattices has been systematically investigated. The well width as well as the period were determined directly by X-ray diffraction. This was accomphshed for the well width by exploiting the high reflectivity from HgTe and the low reflectivity from CdTe for the (002) Bragg reflection. Knowing the well and barrier thicknesses we have been able to set an upper limit on the aver~ge composition of the barriers, Xl, by annealing the superlattice and then measuring the composition of the. resultmg alloy. Xb was shown to decrease exponentially with decreasing barrier width. Xb is appreciably smaller m. narrow barriers due to the increased significance of interdiffusion in the Hg\(_{1-x}\)Cd\(_x\) Te/HgTe interface in narrow barriers. The experimentally determined optical absorption coefficient for these superlattices is compared WIth theoretical calculations. The absorption coefficient was determined from transmission and reflection spectra at 300, 77 and 5 K. Using the thickness and composition of the barriers and wells, and an interface width due to interdiffusion, the complex refractive index is calculated and compared with the experimental absorption coefficient. The envelope function method based on an 8 x 8 second order k . p band model was used to calculate the superlattice states. These results when inserted into Kubo's formula, yield the dynamic conductivity for interband transitions. The experimental and theoretical values for the absorption coefficient using no adjustable parameters are in good agreement for most of the investigated superlattices. Furthermore the agreement for the higher energetic interband transitions is much worse if values for the barrier composition, which are appreciably different than the experimentally determined values, are used. The infrared photoluminescence was investigated at temperatures from 4.2 to 300 K. Pronounced photoluminescence was observed for all superlattices in this temperature range.
KW  - Physik
Y1  - 1993
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-50959
ER  - 
TY  - CHAP
A1  - Bicknell-Tassius, R. N.
A1  - Scholl, S.
A1  - Becker, Charles R.
A1  - Landwehr, G.
T1  - High magnetic field transport in II-VI heterostructures
N2  - In the present work we report the results of magneto-transport measurements on some Hg-based li-VI semiconductor epitaxiallayers grown by molecular beam epitaxy. The transport measurement were carried out at temperatures in the range 0.4 - 4.2 K in magnetic fields up to 10.0 T. Further, we point out the necessity of using multicarrier models for data interpretation and show finally some Shubnikov-de-Haas results on sampies with high mobility carners.
Y1  - 1992
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-37797
ER  -