利用发射光谱探究CO_(2)对MPCVD法生长单晶金刚石质量的影响

Exploring the Effect of CO_(2) on the Quality of Single Crystal Diamond Drown by MPCVD with Optical Emission Spectrum

等离子体发射光谱作为一种非侵入性等离子体诊断手段能有效探测等离子体内部基团的变化信息,对这些信息的分析可以反映等离子体的特性,从而有助于探究影响单晶金刚石生长结果的原因和机理。CO_(2)是一种比O2更安全的气体,近年来在源气体引入CO_(2)生长高质量单晶金刚石的研究日渐增多。本文利用微波等离子体化学气相沉积法在4.2 kW的微波功率下进行单晶金刚石同质外延生长实验,对生长过程中的CH_(4)/H_(2)/CO_(2)等离子体进行了发射光谱诊断,最后结合光谱信息和拉曼光谱表征研究了CO_(2)体积分数对单晶金刚石生长质量的影响,结果发现CO_(2)浓度增加对C_(2)和CH基团强度抑制作用明显,对C_(2)抑制作用最强,这也是导致生长速率下降的主要原因。I(CH)/I(Hα)比值略有增加,说明CO_(2)增加对金刚石前驱物的沉积有促进作用,这在一定程度上减弱了对生长速率的不利影响。拉曼表征结果说明0~5%CO_(2)浓度下的单晶金刚石质量随CO_(2)浓度上升变好,且浓度为5%时,1420 cm−1杂质峰基本消失。

As a non-invasive plasma diagnostic tool,optical emission spectrum(OES)can detect a variety information of radicals in plasma,and it is possible to analyze this information to reflect the characteristics of plasma,which contribute to investigating the cause and mechanism for single crystal diamond(SCD)depositing.CO_(2)is a safer gas than O2,so there have been more and more studies on introducing CO_(2)into source gas for highquality SCD deposition in recent years.In this paper,homoepitaxial SCDs are cultivated by microwave plasma chemical vapor deposition(MPCVD)with an input power of 4.2 kW.CO_(2)is added into CH_(4)/H_(2)plasma,and radicals are diagnosed via OES,and then the effect of CO_(2)concentration on the growth quality of SCDs is investigated by combining OES information and Raman spectroscopy characterization.The results show that the increase in CO_(2)concentration has an obvious inhibitory effect on the intensity of C_(2)and CH radicals,and the strongest inhibitory effect on C_(2)especially,which is also the main reason for the decline in growth rate.The ratio of I(CH)/I(Hα)increased slightly,indicating that the increase of CO_(2)promoted the deposition of diamond precursors,which weakened the adverse effect on the growth rate to a certain extent.The Raman characterization results show that the quality of SCD grown under the concentration of 0~5%CO_(2)improves with the increase of CO_(2)concentration,and the impurity peak of 1420 cm−1 basically disappears when the concentration is 5%.