Effects of annealing conditions and thickness ratio of Si/Al films on the Hall carrier mobility, Al carrier concentration, and nanovoids formed in the metal-induced Si crystallization of Si/Al/Si/SiO2/glass specimens

• Published in: Surface & coatings technology Vol. 205; no. 19; pp. 4672 - 4682
• Main Authors: Peng, Cheng Chang, Chung, Chen Kuei, Wu, Bo Hsiung, Weng, Min Hang, Huang, Chil Chieh, Lin, Jen Fin
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 25.06.2011; Elsevier
• Subjects: Al carrier concentration; Aluminum; Annealing; Carrier density; Carrier mobility; Cross-disciplinary physics: materials science; rheology; Crystallization; Exact sciences and technology; Hall carrier mobility; Halls; Materials science; Metal-induced Si crystallization; Nanostructure; Physics; Sandwich structure; Silicon; Surface treatments; μc-Al grains; Metal-induced Si crystallization; Hall carrier mobility; μc-Al grains; Sandwich structure; Al carrier concentration; Thickness; Annealing; Crystallization; Surface treatments; Silica; Heat treatments
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2011.04.032

In the present study, a-Si/μc-Al/a-Si/SiO2/glass specimens were prepared with various combinations of thicknesses of the μc-Al layer and the two a-Si layers. The effects of μc-Al film thickness, a-Si film thickness, the thickness ratio of Al film to Si films, and the annealing temperature on the metal-induced Si crystallization and void defects formed in the sandwich composite specimens were investigated. A transmission electron microscope (TEM) and an X-ray photoelectron spectroscope (XPS) were used to investigate the diffusion mechanism and efficiency of Si crystallization. When the annealing temperature was sufficiently high, the μc-Al grains diffused into the two adjacent Si layers with a fairly even distribution over the entire sandwich structure. Si crystallization was thus significantly enhanced by the sandwich structure. The Hall carrier mobility of the specimen with a structure of a-Si(500nm)/μc-Al(50nm)/a-Si(500nm) was 80.1cm2/Vs and the Al carrier concentration was 1.5×1018/cm3 at an annealing temperature of 600°C; no voids were found in the sandwich structure. An increase in the top layer (a-Si) thickness is advantageous for Si crystallization; however, an increase in the third layer (a-Si) thickness degrades Si crystallization. For a given Al film thickness, an excessive increase in the thicknesses of the two a-Si layers degrades Si crystallization even at high annealing temperatures. A thick Al film in combination with two thick a-Si layers leads to a high Hall carrier mobility when the annealing temperature is sufficiently high. An increase in the Si/Al thickness ratio increases the Hall carrier mobility and decreases the Al carrier concentration. ► The μc-Al grains diffused into the two adjacent Si layers with a fairly even distribution over the entire sandwich structure. ► The Hall carrier mobility of the specimen annealing at 600°C for of 15 minutes of a-Si(500nm)/μc-Al(50nm)/a-Si(500nm) was 80.1cm2/Vs and the Al concentration was 1.5×1018/cm3; voids were not found in the sandwich structure. ► A thick Al film in combination with two thick a-Si layers leads to a high carrier mobility when the annealing temperature is sufficiently high.