The structural stability is a major difficulty to the large scale application of electronic devices based on hydrogenated amorphous silicon (a-Si:H) and germanium (a-Ge:H). Atomic hydrogen migration occurs in the amorphous network due to the annealing and the accumulation on the wall of voids causes the evolution of hydrogen bubbles. Considerable effort has been made to understand microscopic origin of the mechanisms. In this lecture we investigate the structural stability of a-Si:H, a-Ge:H and a-SiGe:H films obtained by RF sputtering. The appearing of the surface blister during the annealing process was monitored by surface reflection change using laser beam reflection. The onset of blistering was identified with the decreasing of the reflected intensity caused by the outgoing rays reflected at many different angles. The activation energy for the onset of blistering was interpreted by Arrhenius plots. By an FTIR study [1,2] [ of the behavior of the Ge-H and Si-H stretching vibrations it was seen that annealing increases the density of dihydrides residing on the internal surfaces of nanovoids, already present in the as-deposited films, which increase their size because of that. The thermal energy supplied by annealing also favors the break of the weak GeH2 and SiH2 bonds with consequent release inside the cavities of atomic H which then reacts for produce molecular H2. We found Vegard's law-like dependence of the activation energy for blisters on the Ge concentration in amorphous SiGe alloys. Keywords: Blisters; Hydrogen; Amorphous SiGe; Annealing; Sputtering REFERENCES [1] M. Serényi, C. Frigeri, A. Csik, N. Q. Khánh, A. Németh and Z. Zolnai, CrystEngComm, 19 (2017) 1486-1494 [2] C. Frigeri, M. Serényi, Zs. Szekrényes, K. Kamarás, A. Csik, N. Q. Khánh, Sol. Energy, 119 (2015) 225-232
On the arise of molecular hydrogen in the hydrogenated amorphous silicon, germanium and their alloys
C Frigeri
2017
Abstract
The structural stability is a major difficulty to the large scale application of electronic devices based on hydrogenated amorphous silicon (a-Si:H) and germanium (a-Ge:H). Atomic hydrogen migration occurs in the amorphous network due to the annealing and the accumulation on the wall of voids causes the evolution of hydrogen bubbles. Considerable effort has been made to understand microscopic origin of the mechanisms. In this lecture we investigate the structural stability of a-Si:H, a-Ge:H and a-SiGe:H films obtained by RF sputtering. The appearing of the surface blister during the annealing process was monitored by surface reflection change using laser beam reflection. The onset of blistering was identified with the decreasing of the reflected intensity caused by the outgoing rays reflected at many different angles. The activation energy for the onset of blistering was interpreted by Arrhenius plots. By an FTIR study [1,2] [ of the behavior of the Ge-H and Si-H stretching vibrations it was seen that annealing increases the density of dihydrides residing on the internal surfaces of nanovoids, already present in the as-deposited films, which increase their size because of that. The thermal energy supplied by annealing also favors the break of the weak GeH2 and SiH2 bonds with consequent release inside the cavities of atomic H which then reacts for produce molecular H2. We found Vegard's law-like dependence of the activation energy for blisters on the Ge concentration in amorphous SiGe alloys. Keywords: Blisters; Hydrogen; Amorphous SiGe; Annealing; Sputtering REFERENCES [1] M. Serényi, C. Frigeri, A. Csik, N. Q. Khánh, A. Németh and Z. Zolnai, CrystEngComm, 19 (2017) 1486-1494 [2] C. Frigeri, M. Serényi, Zs. Szekrényes, K. Kamarás, A. Csik, N. Q. Khánh, Sol. Energy, 119 (2015) 225-232I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
