Next generation Acoustic Wave Filter Platform

声波装置利用固体材料中比空气中更高的声速，通过压电将电能转换成声能。诸如表面声波（SAW）器件和体声波（BAW）器件之类的器件可以过滤声学域中的高频，并且形成移动的电话基站和雷达的骨干。这将现有的SAW技术限制在2GHz左右。压电材料的导热性也非常有限，这意味着不可能在高功率下工作。为了实现更高频率的器件，人们越来越倾向于创造新的材料组合，村田制作所的“难以置信的高性能”（IHP）SAW滤波器就是明证，该滤波器结合了压电LiTO 3和硅。金刚石将是这项技术的自然延伸，具有所有声波速度中最高的，以及任何电绝缘体中最高的热导率。不幸的是，金刚石和大多数压电体之间的耦合相对较弱，这导致高插入损耗。该项目旨在通过表面活化晶片键合（SAWB）来缓解这一问题，该键合还可以避免金刚石生长的高温和恶劣环境，这些环境会严重损坏压电材料。通过在室温下结合，将有可能在大面积上将联合收割机高性能压电单晶与金刚石结合，以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，而热导率同时解锁了目前任何其他SAW平台无法实现的高功率操作（压电体固有地具有低热导率）。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.