Development of Giant Diamonds from Chemical Vapor Deposition for High-Pressure Research

这笔赠款用于支持一项为期三年的开发计划，该计划旨在通过新的化学气相沉积(CVD)技术制造大尺寸(高达250克拉)的单晶钻石，开发用于钻石砧座(DAC)高压/高温实验的“特制”钻石砧座，以及开发用于华盛顿卡内基研究所地球物理实验室的大容量DAC实验的新垫圈和压力机。对地球深部(下地幔和地核)物质的物理、化学、电气和机械性质以及内部发现的气体的性质的表征巨型气体行星(例如木星和土星)只能在极压(100-350 Gpa)下现场进行，DAC实验已经成功地证明了这一点。金刚石顶锤具有极高的硬度，可在压制单元实验中获得兆巴压力，可在激光加热的极端温度条件下获得高的热扩散率，以及非常适合于X射线衍射和现场高P/T相的光谱询问的光学透明度。目前，DAC实验仅限于分析可容纳在有限尺寸(例如，0.25-2.5克拉)的无瑕疵天然钻石锤内的微小样品尺寸的特性。无瑕疵的天然钻石非常昂贵(0.25克拉的钻石约1000美元，2.5克拉的钻石高达10万美元)，更大的无瑕疵钻石的成本随着克拉重量的增加而平方增加。尚未证明自然界中存在超过25克拉的天然无瑕疵钻石。最近在CIW-GL获得的新一代6 kW微波CVD等离子体系统室被阻止，使快速生长大(10-100 ct)、无瑕疵的单晶钻石成为可能，这可能为极端压力和温度下的材料研究开辟一个新的前沿。价格实惠、结构和光学优化的大钻石将用于试验新的砧座形状和新颖的垫圈设计。此外，CVD生长的钻石可以与嵌入式传感器一起制造，以便为专门的实验(例如，下地幔和核相的磁性、电学和弹性特性表征)提供可用的“设计”砧板。该项目的目标是开发新类型的高压装置，使采样量增加到目前兆巴压力下传统钻石池的100至1000倍。这些进展将促进目前无法用于超高压研究的许多基于X射线的分析技术，包括成功利用主要的新中子(橡树岭的SNS)和世界各地现有的第二代和第三代同步辐射设施(例如，APS/ANL、BNL、ESRF、SPRING-8)所需的技术。这些新型高压室的成功开发将允许在高压地球科学、行星和材料科学中进行新的实验。该项目将吸引两名研究生从事新型仪器设计和矿物物理研究应用，并将为他们在学术界、国家实验室和工业中可能的不同职业做好准备。除了地球科学，对材料在极端压力下的电、光和物理特性的研究有望产生具有深远社会影响的新技术衍生产品(例如，具有热和电磁特性的新型CPU芯片材料，可以适应微电路的持续发展)。***

0550040HemleyThis grant provides support for a three year development program aimed at fabrication of large (up to 250 carat) single crystal diamonds by novel chemical vapor deposition (CVD) techniques, the development of "designer" diamond anvils for high pressure/high temperature experimentation in the diamond anvil cell (DAC), and the development of new gaskets and presses for use in large volume DAC experiments at the Geophyscial Lab, Carnegie Institution of Washington. Characterization of the physical, chemical, electrical and mechanical properties of deep earth (lower mantle and core) materials, and properties of gases found within the interiors the giant gas planets (e.g. Jupiter and Saturn) can only be carried out in situ at extreme pressures ( 100-350 GPa) that have been demonstrated in successful DAC experiments. Diamond anvils offer extreme hardness, allowing for megabar pressures to be obtained in pressed cell experiments, high thermal diffusivity that allows for extreme temperature conditions with laser heating, and optical transparency that is ideal for x-ray diffraction and spectroscopic interrogation of high P/T phases in situ. Currently DAC experiments are limited to analysis of the properties of miniscule sample sizes that can be accommodates within flawless natural diamond anvils of limited size (e.g., 0.25 - 2.5 ct). Flawless natural diamonds are very expensive (ca. $1,000 for a 0.25 ct diamond up to $100K for a 2.5 ct diamond) and larger flawless diamond costs increase quadratically with carat weight. Natural flawless diamonds in excess of 25 carats have not been demonstrated to exist in nature. A recently acquired a next generation 6 kW microwave CVD plasma system chamber at CIW-GL is anticvpated to make possible the rapid growth of large ( 10 - 100 ct), flawless, single crystal diamond that could open a new frontier in the study of materials at extremes of pressures and temperatures. Affordable and structurally and optically optimized larger diamonds would afford experimentation with new anvil culet shapes and novel gasket designs. Also, CVD grown diamonds can be manufactured with embedded sensors to make available "designer" anvils for specialized experiments (e.g., magnetic, electrical, and elastic properties characterization of lower mantle and core phases). The goal of this projects is to develop new classes of high-pressure devices that will allow an increase in sample volumes up to 100 to 1000 times that currently available in conventional diamond cells at megabar pressures. The developments will facilitate numerous x-ray based analytical techniques currently unavailable for ultrahigh-pressure research, including those required for the successful utilization of major new neutron (SNS at Oak Ridge) and existing 2nd and 3rd generation synchrotron radiation facilities worldwide (e.g., APS/ANL, BNL, ESRF, SPring-8). Successful development of these new classes of high-pressure cells will allow for novel experiments in high pressure geoscience, planetary and materials science. The project will engage two graduate students in novel instrument design and mineral physics research applications and will prepare them for a diverse range of possible careers in academia, national laboratories, and industry. Beyond geoscience, the study of the electrical, optical and physical properties of materials at extremes of pressure promises novel technological spin offs with profound societal impact (e.g., new classes of CPU chip materials with thermal and electromagnetic properties that can accommodate continued advances in micro-circuitry). ***