Surface acoustic wave diagnosis of vacancy orbital with electric quadrupoles in silicon. (18th March 2015)

• Record Type: Journal Article
• Authors: Goto, T; Mitsumoto, K; Akatsu, M; Baba, S; Okabe, K; Takasu, R; Nemoto, Y; Yamada-Kaneta, H; Furumura, Y; Saito, H; Kashima, K; Saito, Y
• Is Part Of: Journal of physics. Number 592 (2015)
• Page Start: 012150
• Publication Date: 2015-03-18
• Subjects: Physics -- Congresses; 530.5
• DOI: 10.1088/1742-6596/592/1/012150
• Languages: English
• ISSNs: 1742-6588

Abstract

Abstract: We demonstrate ultrasonic diagnosis of vacancies in boron-doped silicon wafers currently used in device manufacturing. The low-temperature softening of elastic constants measured by surface acoustic waves (SAW) as well as bulk ultrasonic waves is caused by a coupling of elastic strains to electric quadrupoles of the vacancy orbital in silicon wafers. Using interdigital transducers with a comb gap of 2.5 μm on a piezoelectric ZnO film deposited on the (001) surface of the wafer, we observed the softening of 1.9×10 −4 in relative amount of the elastic constant Cs below 2 K down to 23 mK. Taking account of the strong quadrupole-strain interaction, we deduced a small vacancy concentration 3.1×10 12 cm −3 in the surface layer of the wafer within a penetration depth 3.5 μm of the SAW.