Optoelectronic and structural properties of a-Ge1−xCx:H prepared by rf reactive cosputtering

Abstract

Optoelectronic, structural, and mechanical properties of hydrogenated amorphous germanium carbon (a-Ge 1Ϫx C x :H) alloys are presented. The films were prepared by the rf cosputtering technique using graphite-germanium composite targets. Films with carbon contents in the 0Ͻx Ͻ1 range were prepared under the same conditions used to obtain a-Ge:H films with good optoelectronic properties. The trends of the optical gap, infrared absorption, dark conductivity, and mechanical stress as a function of the carbon content suggest that the properties of films with low carbon concentration are mainly controlled by the incorporation of sp 3 hybridized carbon. These films have good optoelectronic and structural properties. As the carbon content increases, the properties of the films are determined by the concentration of sp 2 carbon sites.

Characterization and Properties of Ge1–x–Cx:H Compounds Obtained by X‐ray CVD of Germane/Ethyne Systems: Effect of the Irradiation Dose

“…The three bands obtained at about 2000 cm -1 , 2025 cm -1 , and 2058 cm -1 are certainly attributable to the stretching vibrations of Ge-H bonds in the GeH n (n = 1-3) groups, [7,15,25,[37][38][39][40] but individual attributions can only be attempted. On the basis of our results, [32] and literature data, [7,15,25,[37][38][39][40][41][42][45][46][47] the band around 2025 cm -1 can be attributed to GeCGeH 2 or GeC 2 GeH, the band at about 2000 cm -1 to GeH 2 vibrating in inner cavities, or GeC 2 -GeH, and the band around 2058 cm -1 to GeH 3 , C 2 GeH 2 , or C 3 GeH. A further deduction can be made if it is assumed (as deduced from IR spectra) that hydrogen is bound to carbon mainly as CH groups.…”

“…[21,37] In the wavenumber region between 500 cm -1 and 900 cm -1 , the interpretation of the spectra is complicated by the presence of several signals leading to broad overlapped bands due to the GeCH n (n=1,2) and GeH 2 bending modes, the Ge-C stretching, the CH 2 rocking, and Ge-H wagging modes. [1,7,21,37,40,42] The possible shift of vibrational modes due to changes in the environment must also be taken into account. There is no complete agreement on the single assignments: Vilcarromero et al [7] found two bands at 560 cm -1 and 620 cm -1 in the spectrum of a-GeC:H alloy, obtained with the rf co-sputtering technique, which were assigned to the Ge-H wagging mode and to the Ge-C stretching mode, respectively.…”

“…[1,7,21,37,40,42] The possible shift of vibrational modes due to changes in the environment must also be taken into account. There is no complete agreement on the single assignments: Vilcarromero et al [7] found two bands at 560 cm -1 and 620 cm -1 in the spectrum of a-GeC:H alloy, obtained with the rf co-sputtering technique, which were assigned to the Ge-H wagging mode and to the Ge-C stretching mode, respectively. [7,38] , and 660 cm -1 attributed to asymmetrical stretching of C-Ge-C, GeH wagging, Ge-(CH 2 ) 4 stretching, and C-C-Ge stretching, [19,21,37] respectively, whereas Drüsedau et al [1] attribute a band at 590 cm -1 to the superimposed signals of Ge-C stretching and GeH wagging shifted as a consequence of the environmental change due to the presence of carbon.…”

“…In the regions between 2800 cm -1 and 3000 cm -1 , and around 2000 cm -1 the stretching of C-H bonds and Ge-H bonds, respectively occur, whereas between 1200 cm -1 and 1500 cm -1 , the bond bending signals of C(H) n groups are usually found. [1,7,21,[36][37][38][39][40][41][42][43][44] The fourth region, between 400 cm -1 and 1200 cm -1 is characterized by broad and overlapping bands attributable to stretching, bending, wagging, and rocking vibrations of various bond systems such as Ge-H, Ge-C, CH 2 , and Ge-C-C. ). [7,21,[37][38][39][40][41][42][43][44] Signals attributable to the stretching of the C-H bond in the CH 3 group are only observed in the spectrum of the solid obtained from irradiation of the mixture with 10 % ethyne after 1.5 h of radiolysis.…”

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

“…Thus the thermal stability for Ge 1Àx C x films is an important issue for their reliable long-term performance. Up to the present, some optical, electrical, and structural properties have already been reported for the Ge 1Àx C x films, using different techniques such as chemical vapor deposition [7,8], activated reactive evaporation (ARE) [9,10], glow discharge [11,12], and reactive sputtering of either germanium in hydrocarbon atmosphere [13,14] or mixed germanium/ carbon targets in hydrogen and/or argon atmosphere [15][16][17]. However, so far, there have been very few reports on the thermal stability for Ge 1Àx C x films, and the effects of the annealing on their bonding structures, optical and mechanical properties have not been well explored yet.…”