Molecular beam mass spectrometry of microwave activated plasmas used in diamond chemical vapour deposition

用于金刚石化学气相沉积的微波激活等离子体的分子束质谱分析

• 批准号: EP/D074924/1
• 负责人: Paul May
• 金额: $ 47.34万
• 依托单位: University of Bristol
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2006
• 资助国家: 英国
• 起止时间: 2006 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FD074924%2F1
• 关键词: Molecular; beam; mass; spectrometry; microwave

It is now possible to deposit thin coatings of diamond onto a substrate of choice using a gas phase chemical reaction called 'Chemical Vapour Deposition' (CVD). In CVD, a carbon containing molecule, such as methane gas, is passed into a vacuum chamber along with a mixture of other gases, such as hydrogen and argon, where they are supplied with energy from a microwave generator. This energy heats the gases and causes them to break apart and diffuse to a surface to form a diamond coating. The longer the reaction continues, the thicker the diamond coating becomes. Such diamond coatings are beginning to find applications in cutting tools, wear-resistant coatings, medical implants, optics and heat spreaders. But what is missing is a deeper understanding of the chemistry behind the CVD growth process. Without this, the film properties cannot be optimised and process development becomes a matter of trial-and-error. The Bristol diamond CVD group has a great deal of experience in understanding the chemistry of the complex plasmas used to deposit diamond films. In 1994 we designed and built the first generation of an apparatus capable of measuring the concentrations of the important stable and radical species within these plasmas during diamond deposition - this is a molecular beam mass spectrometer, which can suck gas from the plasma through a sampling probe and pass it into a detector which identifies each gaseous component. We have used this apparatus very successfully to understand the processes occurring in various diamond-growing gas mixtures, and have published 10 papers based on its findings. However, this unique apparatus has a number of limitations, which became most obvious when we recently began trying to probe commercially more important microwave plasma environments. We now wish to build on these lessons and develop a new, more versatile, and much more sensitive, molecular beam mass spectrometer (MBMS) experiment. What new science will an improved 2nd generation reactor-MBMS system enable? For the first time, we will be sampling process gas at the surface of the growing diamond film in a MW reactor / which has been designed to approach industry standards. We anticipate a >1000x sensitivity gain compared to our previous apparatus, as a result of careful consideration of orifice sizes, propagation distances in the various pressure regions, much improved pumping speeds, and the incorporation of a properly-designed chopper. Just in the context of the basic CH4/H2 (and CH4/Ar/H2) gas mixtures, this should afford us the opportunity to make the first careful studies of the relative (and absolute) abundances of reactive species like C, CHx, C2, C2Hx, C3, C3Hx / in parallel, and as a function of process conditions. The plasma chemical model and thermochemical reaction mechanism that we have developed thus far, and which has been used in all of our most recent comparisons with experiment, still has a number of recognised limitations / which can be tested, validated or improved, as necessary, by experiments of this kind. We can also use the new system to probe gas mixtures that have so far eluded diagnosis, due to the pressure being too high or lack of sensitivity for low concentration species. For example we wish to study the role of B and N in the gas phase, for use in doping diamond to make electronic devices. We also want to study the role of Ar and CH4 in depositing so-called ultrananocrystalline diamond films, which are currently being suggested as candidates for biochemical sensors and other detectors.

现在可以使用称为“化学气相沉积”（CVD）的气相化学反应将金刚石的薄涂层存款到所选的基底上。在CVD中，含碳分子（例如甲烷气体）与其它气体（例如氢气和氩气）的混合物一起沿着进入真空室，在真空室中，它们由微波发生器提供能量。这种能量加热气体，使它们分解并扩散到表面，形成金刚石涂层。反应持续的时间越长，金刚石涂层变得越厚。这种金刚石涂层开始在切削工具、耐磨涂层、医疗植入物、光学和散热器中找到应用。但缺少的是对CVD生长过程背后的化学过程的更深入理解。没有这一点，薄膜性能就无法优化，工艺开发就变成了一个试错的问题。布里斯托金刚石CVD小组在理解用于存款金刚石薄膜的复杂等离子体的化学方面具有丰富的经验。1994年，我们设计并制造了第一代能够测量金刚石沉积过程中这些等离子体中重要的稳定和自由基物质浓度的设备-这是一种分子束质谱仪，它可以通过采样探针从等离子体中吸取气体，并将其传递到检测器中，以识别每种气体成分。我们已经非常成功地使用这种装置来了解各种金刚石生长气体混合物中发生的过程，并根据其发现发表了10篇论文。然而，这种独特的设备有许多局限性，当我们最近开始尝试探测商业上更重要的微波等离子体环境时，这些局限性变得最为明显。我们现在希望在这些经验的基础上，开发一种新的、更通用的、更灵敏的分子束质谱仪（MBMS）实验。改进的第二代反应堆-MBMS系统将实现什么新科学？我们将首次在MW反应器中生长的金刚石膜表面对工艺气体进行采样，该反应器的设计符合行业标准。与我们以前的设备相比，我们预计灵敏度增益> 1000倍，这是由于仔细考虑了孔尺寸、在各个压力区域的传播距离、大大提高的泵送速度以及适当设计的斩波器的结合。仅在基本的CH 4/H2（和CH 4/Ar/H2）气体混合物的情况下，这应该为我们提供机会来并行地并且作为工艺条件的函数对反应性物种如C、CHx、C2、C2 Hx、C3、C3 Hx/的相对（和绝对）丰度进行首次仔细研究。等离子体化学模型和热化学反应机制，我们已经开发到目前为止，并已被用于我们所有的最新比较与实验，仍然有一些公认的局限性/可以测试，验证或改进，必要时，通过这种实验。我们还可以使用新的系统来探测迄今为止由于压力过高或对低浓度物质缺乏灵敏度而无法诊断的气体混合物。例如，我们希望研究B和N在气相中的作用，用于掺杂金刚石以制造电子器件。我们还想研究Ar和CH 4在沉积所谓的超纳米晶金刚石薄膜中的作用，这些薄膜目前被建议作为生物化学传感器和其他探测器的候选物。

项目成果

Deep reactive ion etching of silicon moulds for the fabrication of diamond x-ray focusing lenses

• DOI: 10.1088/0960-1317/23/12/125018
• 发表时间: 2013-11
• 期刊: Journal of Micromechanics and Microengineering
• 影响因子: 2.3
• 作者: A. Malik;O. Fox;L. Alianelli;A. Korsunsky;R. Stevens;I. Loader;M. Wilson;I. Pape;K. Sawhney;P. May

Carbon Based Nanomaterials: Handbook

碳基纳米材料：手册

• 发表时间: 2010
• 作者: Ali, Nasar;Oechsner, Andreas;Ahmed, Waqar
• 通讯作者: Ahmed, Waqar

Electrospray Deposition of Diamond Nanoparticle Nucleation Layers for Subsequent CVD Diamond Growth

• DOI: 10.1557/proc-1203-j17-27
• 发表时间: 2009
• 期刊: MRS Proceedings
• 作者: O. Fox;J. Holloway;G. Fuge;P. May;M. Ashfold

A planar refractive x-ray lens made of nanocrystalline diamond

• DOI: 10.1063/1.3517060
• 发表时间: 2010-12-15
• 期刊: JOURNAL OF APPLIED PHYSICS
• 影响因子: 3.2
• 作者: Alianelli, L.;Sawhney, K. J. S.;Wilson, M. C.
• 通讯作者: Wilson, M. C.