Channeling Measurements on Deuterium Implanted Silicon
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CHANNELING MEASUREMENTS ON DEUTERIUM IMPLANTED SILICON B. BECH NIELSEN Institute of Physics, University of Aarhus DK-8000 Aarus C, Denmark
ABSTRACT The channeling technique has been used to study the lattice location of deuterium ion-implanted into silicon. Compared to earlier measurements by Picraux and Vook, the temperature range has been Ttendeý from 30 to 500 K, and the dose has been decreased down to - 8 x 10 D/cm . The implantation was performed at 30 K gnd at an energy of 10 keV. The channeling analysis was done using the d( He,p) 4He nuclear reaction. Angular scans were measured along the , , axis and the 100, (110), (111) planes, Experiments were carried out on the implanted sample (30K) and after annealing to 200 and 500 K. In the as-implanted sample, 80% of the deuterium is located close to the bond center, whereas the remaining 20% is placed at the tetrahedral site. The deuterium sites change after annealing to 200 and 50OK, and the nature of these annealings stages will be discussed. INTRODUCTION In 1975 Spear and Le Comber 1 succeeded in doping hydrogenated amorphous silicon. This led to an increased'interest in the properties of hydrogen in silicon with the promising possibility of producing effective low-cost semiconductor devices based on the amorphous material. The ability of hydrogen to passivate deep-level centers in Si such a? Irpnsition metal impurities and lattice defects is now well established . Passivation of acceptors in silicon samples exposed to a hydrogen plasma have been demonstrated in several papers . Infrared absorption spectroscopy has given valuable information concerning the bonding of hydrogen implantf ed in silicon . Stein found a major Si-H.- stretch frequency at 1990 ca 1 (close to those of silane (SiH 4)) after implantation of hydrogen at 80K. The activation energy of annealing of thig absorption line was found to coincide with thfl of the neutral vacancy (or possibly the doubly charged positive vacancy ). On this basis Stein interpreted the 1990 cmline as the Si-H stretch frequency originating from the hydrogen saturation of a dangling bond. The detailed lattice location of 1hydrogen implanted in silicon has been studied by Picraux and Vook by means of channeling measurements following room temperature implantation of deuterium. Their measurements were also performed at room temperature, and they concluded that deuterium is predominantly located in a single site displaced 1.6 A from a Si atom in the backbonding direction. The main 1 yaf 1 ?f the theoretical work has involved calculations small clusters , but also self consistent pseudopotential methods have been used. In spite of these efforts it is still not clear, where hydrogen is locat~d in the perfect lattice. Calculations based on extended Huckel theory suggest the tetrahedral (T) position as the solution site of atomic hydrogen in the neutral charge state. Thi? 3 conclusion is in agreement with the results of Mainwooo, and Stoneham but in contrast to the M-site sugges•td by Corbett et al. and the backbonding site o
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