Abstract
Whiskers are a new material that is characterized by high structural perfection, chemical resistance and strength which reaches the theoretically possible limit for crystals of small transverse dimensions. The test whiskers were synthesized by the method of chemical transport reactions in a closed bromide system using gold as the initiator of growth. The crystals were irradiated by protons with an energy of 6 MeV and doses of 5 · 10 13 , 10 15 and 1 · 10 17 p + /cm 2 at 40 ° C in a U − 120 cyclotron. The effects of proton irradiation and high magnetic fields on the magnetoresistance of Si 1 − x Ge x ( x = 0,03) whiskers in the 4,2—300 K temperature range has been studied. A slight decrease in the electrical resistance of the crystals in the 4,2—40 K temperature range during irradiation with small proton doses and a significant increase in their resistance in the entire investigated temperature range for a dose of 1·10 17 p + /cm 2 have been found. The ionization energy of the impurity atoms in different magnetic fields has been calculated. It has been revealed that the energy level of the impurity depends on the magnetic field but slightly which in turn indicates a independence of the concentration of holes on the magnetic field. It has been shown that a significant magnetoresistance at all studied temperatures was due to the magnetic field − caused decrease in the mobility of free charge carriers (holes). It has been found that the concentration of holes depends on magnetic field but a little. Conclusion has been made about a negligible expansion of the band gap in magnetic fields of up to 8 T.
Highlights
Mechanical sensors based on Si−Ge whiskers / R
Whiskers are a new material that is characterized by high structural perfection, chemical resistance and strength which reaches the theoretically possible limit for crystals of small transverse dimensions
The test whiskers were synthesized by the method of chemical transport reactions in a closed bromide system using gold as the initiator of growth
Summary
Нитевидные кристаллы — это новый материал, который характеризуется высоким структурным совершенством, химической стойкостью, прочностью, которая для кристаллов небольших поперечных размеров достигает теоретически возможного предела. Кристаллы облучали протонами с энергией 6 МэВ и дозами 5 · 1013, 1015 и 1 · 1017 р+/см−2 при 40 °С на циклотроне У−120. Обнаружено незначительное уменьшение электрического сопротивления кристаллов в температурной области 4,2—40 К в процессе облучения малыми дозами протонов и существенное увеличение сопротивления во всей исследуемой температурной области при облучении дозой 1 · 1017 р+/см. Что существенное магнетосопротивление при всех исследованных температурах связано с магнитополевым уменьшением подвижности свободных носителей заряда (дырок). Установлено, что концентрация дырок практически не зависит от магнитного поля. Одним из таких новых материалов являются нитевидные кристаллы, которые характеризуются высоким структурным совершенством, химической стойкостью, прочностью, которая для кристаллов небольших поперечных размеров достигает теоретически возможного предела [1]. Цель работы — исследование магнетосопротивления НК Si0,97Ge0,03, облученных разными дозами протонов
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