Structural Studies on Hydrogenated Amorphous Germanium-Carbon Films Prepared by RF Sputtering

Abstract

Various techniques, used to optimize on-line principal component analysis, are investigated by methods of statistical mechanics. These include local and global optimization of node-dependent learning-rates which are shown to be very efficient in speeding up the learning process. They are investigated further for gaining insight into the learning rates' time-dependence, which is then employed for devising simple practical methods to improve training performance. Simulations demonstrate the benefit gained from using the new methods.

Transition from Amorphous Semiconductor to Amorphous Insulator in Hydrogenated Carbon−Germanium Films Investigated by Raman Spectroscopy

“…Recently, investigations on carbon−germanium films performed by Raman spectroscopy have been also reported. The films were fabricated by a variety of techniques including rf cosputtering of germanium and carbon in argon (plus hydrogen) plasma, , dc magnetron sputtering in argon plasma, , rf magnetron sputtering of Ge in plasma generated in a mixture of methane, hydrogen, and argon, and molecular beam epitaxy (MBE). , In all the cases the Raman spectra reveal two well-separated regions that can be attributed to Ge−Ge (50−350 cm -1 ) and C−C (1200−1800 cm -1 ) modes. In general, however, there is no evidence of any band related to Ge−C bonds.…”

Annealing effects on the bonding structures, optical and mechanical properties for radio frequency reactive sputtered germanium carbide films

“…The absorption band located at $2900 cm À1 is related to the C-H n (n = 1, 2, 3) stretching modes [5,16], which is not significantly affected by annealing when T a is not over 400 8C. This high thermal stability of C-H bonds, compared to Ge-H ones, is attributed to that a C-H bond has a higher bonding energy (4.3 eV) than that (3.0 eV) of a Ge-H bond [23]. However, as T a further increases from 400 to 700 8C, the intensity of C-H bonds gradually decreases, caused by the disruption of C-H bonds at T a above 400 8C.…”

“…The relief of the compressive stress in film after annealing at T a < 400 8C can be attributed to the thermal relaxation of the constituent atoms in film. However, at T a > 400 8C, a substantial increase in the compressive stress may be associated with an increase in the number of Ge-C bonds, resulting in a large lattice distortions due to a large difference in atomic radii between Ge (1.22 Å ) and C (0.77 Å ) [23]. The broad Ge-C (Fig.…”

“…4 shows the Raman spectra for Ge 1Àx C x films annealed at different T a , wherein a peak around 290 cm À1 originating from GeGe transverse optical (TO) mode appears, which indicates the presence of Ge-Ge bonds in film [23]. This peak becomes strong and narrow with increasing T a up to 400 8C, which may be caused by enhancing the structural order in the germanium sub-network in film due to the thermal relaxation of the constituent atoms in film at their low stress sites [23]. However, as T a further increases from 400 to 700 8C the Ge-Ge peak becomes weak and wide, as a result of the degradation in structural order.…”