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Superfluid helium acoustic microscopy

Thesis/Dissertation ·
OSTI ID:5480904
This dissertation describes the development of an acoustic microscope operating in superfluid helium at temperatures less than 0.1K. The acoustic microscope uses sound waves, brought to a focus in a liquid, to image a sample. The lateral resolution of the microscope is approximately equal to the wavelength of the sound in the liquid. Low temperature superfluid helium is the ultimate fluid for acoustic microscopy because of its extremely small acoustic attenuation, allowing short wavelength and high resolution imaging. The present resolution of the helium acoustic microscope is 200 A using 8 GHz sound waves. The wavelength in helium at this frequency is only 300 A, twenty times shorter than red light. Several images are presented, including biological and integrated circuit samples. Comparisons are made with other forms of high resolution microscopy, specifically the scanning and transmission electron microscopes. By virtue of its contrast mechanisms and high resolution, the helium acoustic microscope can image many sample features that cannot be seen in other ways.
Research Organization:
Stanford Univ., CA (USA)
OSTI ID:
5480904
Country of Publication:
United States
Language:
English