tailieunhanh - Báo cáo hóa học: " Relationship between structural changes, hydrogen content and annealing in stacks of ultrathin Si/Ge amorphous layers"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Relationship between structural changes, hydrogen content and annealing in stacks of ultrathin Si/Ge amorphous layers | Frigeri et al. Nanoscale Research Letters 2011 6 189 http content 6 1 189 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access Relationship between structural changes hydrogen content and annealing in stacks of ultrathin Si Ge amorphous layers 1 2 2 3 2 4 1 Cesare Frigeri Miklós Serényi Nguyen Quoc Khánh Attila Csik Ferenc Riesz Zoltán Erdélyi Lucia Nasi Dezso László Beke4 Hans-Gerd Boyen5 Abstract Hydrogenated multilayers MLs of a-Si a-Ge have been analysed to establish the reasons of H release during annealing that has been seen to bring about structural modifications even up to well-detectable surface degradation. Analyses carried out on single layers of a-Si and a-Ge show that H is released from its bond to the host lattice atom and that it escapes from the layer much more efficiently in a-Ge than in a-Si because of the smaller binding energy of the H-Ge bond and probably of a greater weakness of the Ge lattice. This should support the previous hypothesis that the structural degradation of a-Si a-Ge MLs primary starts with the formation of H bubbles in the Ge layers. Introduction Hydrogenated a-Si and a-Ge layers are key materials for employment in nano structures used . in the technology of multi-junction solar cells as a-Ge acts as the low-band gap absorber while a-Si acts as the high-band gap one thus allowing a better exploitation of the solar spectrum and the achievement of higher efficiencies 1 . However the a-SiGe alloy is now the material of choice as the low-band gap absorber 2-4 . It allows a higher degree of freedom as regards the choice of the band gap as the latter one can be tailored over some range by changing the Si Ge ratio 2 4 . The a-SiGe alloy can be realized from a sequence of thin a-Si and a-Ge layers by intermixing them 1 5 6 which is obtained by heat treatments. The latter treatments are often also used for activating dopants. Previous studies have shown that the hydrogen content and .