Next generation Acoustic Wave Filter Platform

声波装置利用压电效应将电能转化为声能，从而利用固体材料中比空气中更高的声速。表面声波（SAW）和体声波（BAW）等设备可以过滤声波域的高频，构成移动电话基站和雷达的骨干。不幸的是，压电材料并不能表现出最高的声波速度，而像金刚石这样的高速材料也不会表现出压电性。这将现有SAW技术限制在2GHz左右。压电材料也有非常有限的导热性，这意味着在高功率下操作是不可能的。创造新材料组合以实现更高频率器件的动力越来越大，Murata的“难以置信的高性能”（IHP） SAW滤波器证明了这一点，该滤波器结合了压电LiTO3和硅。金刚石将是这项技术的自然延伸，具有最高的声波速度和最高的导热性。不幸的是，金刚石与大多数压电材料之间的耦合相对较弱，这导致了高的插入损耗。该项目旨在通过表面活化晶圆键（SAWB）来缓解这一问题，该项目还绕过了金刚石生长的高温和恶劣环境，这些环境会严重损害压电材料。通过在室温下的键合，将有可能将高性能压电单晶与金刚石大面积结合，从而获得无与伦比的性能。金刚石的最高声波速度提供了高频操作，而导热性同时开启了高功率操作，这是目前任何其他SAW平台都无法实现的（压电材料固有的低导热性）。该平台将具有从5G基站收发器到量子存储器的多种应用。

Acoustic wave devices exploit the higher speed of sound in solid materials than air by converting electrical energy into acoustic energy by piezoelectricity. Devices such as Surface Acoustic Wave (SAW) devices and Bulk Acoustic Wave (BAW) devices can filter high frequencies in the acoustic domain and form the backbone of mobile telephony base stations and radar.Unfortunately, piezoelectrics do not exhibit the highest acoustic wave velocities, and high velocity materials such as diamond do not exhibit piezoelectricity. This limits incumbent SAW technologies to around 2GHz. Piezoelectrics also have very limited thermal conductivity which means that operation at high powers is not possible.There is an increasing drive to create new materials combinations to realise higher frequency devices as evidenced by Murata's "Incredibly High Performance" (IHP) SAW filter which combines the piezoelectric LiTO3 and silicon. Diamond would be a natural extension of this technology with the highest of all acoustic wave velocities as well as the highest thermal conductivity of any electrical insulator. Unfortunately, the coupling between diamond and most piezoelectrics is relatively weak which leads to high insertion loss. This project aims to alleviate this issue with a Surface Activated Wafer Bond (SAWB), which also circumvents the high temperature and harsh environment of diamond growth which can significantly damage piezoelectric materials. By bonding at room temperature, it will be possible to combine high performance piezoelectric single crystals with diamond over large areas for unrivalled performance. The superlative acoustic wave velocity of diamond provides for high frequency operation whilst the thermal conductivity simultaneously unlocks high power operation currently unavailable to any other SAW platform (piezoelectrics are inherently of low thermal conductivity). This platform will have multiple applications from 5G base station transceivers to quantum memories.