Research on Laboratory Testing Features of Chemical Vapor Deposition in Overgrowth Diamonds
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摘要: 再生钻石是使用化学气相沉积法（CVD）以天然钻石为基底再生长合成钻石层，得到具有整体外观的钻石产品。由于再生钻石含有天然钻石的氮杂质信息，传统的合成钻石排查方法和检测流程已不再适用于再生钻石的检测。本文对实验室检出的一颗再生钻石进行了详尽的宝石学测试分析，以建立再生钻石的最佳检测方案。结果显示：常规的显微观察、钻石仪器排查以及红外光谱测试都不能将再生钻石检出。DiamondViewTM多方位发光图像观察该样品呈现清晰的发光分层现象，上层为红色荧光与蓝绿色磷光，下层为深蓝色荧光与惰性磷光；红外透射光谱分区域定点扫描样品上层为Ⅱa型钻石，下层为Ⅰa型钻石；紫外可见吸收光谱分析和光致发光光谱测试显示样品同时具有N3和高浓度[Si-V]-缺陷。综合判定该样品亭部的下半部分为天然钻石，亭部的上半部分和冠部为CVD合成钻石，CVD层厚度约740μm。作为我国首例报道的再生钻石，与国外已报道的同类型样品相比，该样品中分层界限不可见，且合成层厚度呈现明显增长。研究认为，应用多方位发光图像分析及光谱测试技术是再生钻石检测的关键。Abstract:
BACKGROUNDOvergrowth diamond refers to the product of thick CVD synthetic diamond layer grown on a natural diamond with the whole appearance. Since overgrown diamonds contain information on the nitrogen impurities of natural diamonds, traditional synthetic diamond screening methods and testing procedures are no longer applicable to the detection of overgrown diamonds. OBJECTIVETo gemologically test an overgrowth diamond sample in order to investigate the full identification features and to propose the optimum detection strategy. METHODSMinspecting, screening instruments testing, UV-Vis/FTIR/PL spectra examinations, as well as fluorescence and phosphorescence observation under deep UV excitation are carried out. RESULTSThe sample cannot be identified by traditional microscopic observation, diamond instrument screening, and infrared spectra measurement. The sample has a distinct boundary that is separated by different luminescence under DiamondViewTM. The upper layer displays red fluorescence and greenish blue phosphorescence, while the lower layer shows deep blue fluorescence and no phosphorescence. Infrared spectroscopic analysis shows that the upper layer is type Ⅱa and the lower layer is type Ⅰa diamond. The UV-Vis absorption and photoluminescence spectra confirmed the coexistence of N3 centers and a high level of[Si-V]- defects in the diamond. CONCLUSIONSIt was confirmed that the lower part of the sample is natural and the upper part of the sample is CVD synthetic layer with a thickness around 740μm. The first overgrowth diamond reported domestically was compared to the same type of samples reported abroad. The existence of a boundary are missing and the thickness of the CVD layer increased significantly in this sample. The innovative application of the multidirectional luminescence imaging and spectroscopic analyses is the key to laboratory testing of overgrowth diamond. -
Key words:
- overgrowth diamond /
- CVD synthetic diamond /
- spectroscopic testing /
- luminescence imaging
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