Study of dissipative quantum state by means of high-frequency ultrasonic devices processed by micromachining

在低温弹性常数和超声衰减系数的测量中，我们通常使用各种压电换能器来产生和检测超声信号。在这项工作中，我们试图利用加工技术来研制高频换能器。首先，对倒台型晶体的制备进行了基本工艺研究。在150 MHz以上的基模频率下，传统的AT切割石英晶体的有限中心区厚度被刻蚀到5μm。我们成功地制作了基频260 MHz的空白器件，并用倒台式AT-Cut石英换能器测量了Ce_3Pd_20Ge_6的弹性常数C44。另一方面，我们发现用石英晶体在同一工艺中实际刻蚀LiNbO_3和LiTaO_3是困难的。利用LiNbO_3制成的倒台式尖端，开发了使用纳米颗粒流体的先进技术。

We usually use a variety of piezoelectric transducers for generation and detecting of ultrasound signals in low-temperature measurements of elastic constants and ultrasonic attenuation coefficients. In this work, we tried to make high-frequency transducers developed by using processing technology. At first, basic process is involved in manufacturing inverted mesa-type crystals. The thickness of limited central area of conventional AT-cut quarts crystal is etched down to 5 μm for desired frequency over 150 MHz with fundamental mode. We successfully made devices with fundamental frequency of 260 MHz with blanks and applied to measure the elasticconstant C44 in Ce_3Pd_20Ge_6 with inverted mesa-type AT-cut quarts transducer. On the other hand, we found it is difficult to etch practically the LiNbO_3 and LiTaO_3 in thesame process with quarts crystal. The advanced technique using nano-particle fluid is nowdeveloped utilizing for inverted mesa-type tips made of LiNbO_3.