Amorphous silicon produced by ion implantation: Effects of ion mass and thermal annealing

Abstract

Characterization of the two optical states of amorphous Si produced by ion implantation is extended to include electron paramagnetic resonance, fundamental absorption edge, and density measurements in addition to infrared reflection. It is found that the properties of the two a-Si states are not dependent upon the mass of the incident ion (12C, 29Si, 31P, 120Sn) or upon the anneal temperature for 400 °≤TA≤600 °C. The dangling-bond density drops about a factor of 2 when the a-Si makes a transition between the two states. The absorption coefficient also drops by more than a factor of 5, but the density of the a-Si does not change when the transition occurs. The transition between states was not completed at TA=300 °C, so the annealing mechanism may be temperature dependent.

Pressure-enhanced crystallization kinetics of amorphous Si and Ge: Implications for point-defect mechanisms

“…One sample was pre-annealed at 523°C for about 9 minutes and then placed on the heater block for SPEG. This pre-annealing treatment almost completely relaxes the a-Si, according to the spectroscopy results of Waddell et al 50 and the calorimetry results of Donovan et al 44 (note time axis in Fig. 15).…”

“…On the basis of spectroscopic studies 48 , the two point defects that have been proposed are dangling bonds 48 (threefold-coordinated atoms) and floating bonds 49 (fivefold-coordinated atoms); both are analogous to the two predominant point defects in crystals (vacancies and interstitials). Waddell et al 50 have shown that for self-implanted a-Si, the concentration of spectroscopic defects decreases during structural relaxation by about a factor of 2 from 2x10 19 cm -3 after annealing at 500 o C.…”

“…Among the estimates of the defect density in a-Si, the lowest is ~ 10 19 /cm 3 from the spectroscopy work of Waddell et al 50 in a fully relaxed amorphous phase formed by implantation. Other estimates are as high as a few atomic percent 46 .…”

“…This identification of parameters is subject to the assumptions discussed above. If [D o ] is taken to be the density of unpaired electrons in the bulk of a-Si, measured to be ≈ 10 19 /cm 3 with electron spin resonance 50 , then to fit the data α must be about 0.3 -0.5 %.…”

Dynamics of Change in Electrical Conductivity of Ion Irradiated Amorphous Silicon.

“…Amorphous silicon (a-Si), a material with potential for application for SOT and large grained polysilicon TFT technologies, is also thought to be an ideal candidate for study of amorphous solids characterized as continuous random networks. Much work has been done in studying relaxation behavior in amorphous silicon, and many properties of a-Si were shown to be dependent on its degree of relaxation [1][2][3]. Recently, relaxation has been interpreted to occur by annihilation of point defects [3].…”