Crystal Quality of Different Surface Morphologies in Sapphire by EFG Method

doi:10.16553/j.cnki.issn1000-985x.2025.0202

Abstract

Abstract: In this study，by optimizing the process parameters in the early stage of sapphire growth by the edge-defined film-fed growth （EFG） method，a special interface structure with stepped morphology was successfully induced on the crystal surface. Multiple characterization techniques were employed to systematically compare the crystal quality between the stepped interface and the flat interface. The results show that the full width at half maximum of Raman spectrum，the full width at half maximum of X-ray diffraction（XRD） single crystal rocking curve and the spectral transmittance of the stepped interface samples are better than those of the flat interface samples. In addition，the average bubble sizes of the stepped interface regions are 42.98 μm×37.27 μm and 37.90 μm×35.23 μm，respectively，which are significantly smaller than those in the flat interface （68.04 μm×55.70 μm and 52.03 μm×36.89 μm）. The stepped interface also demonstrates lower bubble distribution density，oxygen vacancy concentration and internal stress. Scanning electron microscope observation reveales that the growth steps on the stepped interface are parallel，straight and closely spaced，whereas the growth steps on the flat interface are irregular and loose，with distance of the growth steps on the flat interface is larger than that on the stepped interface. In summary，the stepped interface performs better in crystal structure integrity and optical properties. This study provides a novel process strategy for the controlled growth of high-quality sapphire crystals using the EFG method.

Key words: sapphire crystal; EFG method; crystal quality; bubble; growth step

CLC Number:

O782

SHU Jun, NIE Lingda, ZHAO Peng, XUE Longfei. Crystal Quality of Different Surface Morphologies in Sapphire by EFG Method[J]. Journal of Synthetic Crystals, 2026, 55(2): 281-290.

Figures/Tables 19

Fig.1 Image of sapphire plate A grown by EFG method

Fig.2 Image of sapphire plate B grown by EFG method

Table 1 Raman FWHM corresponding to A-1，A-2，A-3，A-4，B-1 and B-2

Sample ID	Flat interface A-1	Flat interface A-2	Stepped interface A-3	Flat interface A-4	Flat interface B-1	Stepped interface B-2
Raman FWHM/cm^-1	3.66	3.71	3.38	3.58	3.48	3.09

Fig.3 XRD single crystal rocking curves of flat interface A-2 （a） and stepped interface A-3 （b）

Fig.4 XRD single crystal rocking curves of flat interface B-1 （a） and stepped interface B-2 （b）

Table 2 Raman FWHM and XRD FWHM of A-2，A-3，B-1 and B-2

Sample ID	Flat interface A-2	Stepped interface A-3	Flat interface B-1	Stepped interface B-2
Raman FWHM/cm^-1	3.71	3.38	3.48	3.09
XRD FWHM/（″）	100.8	68.4	90.0	46.8

Fig.5 Ultraviolet transmittance of A-2 and A-3 （a） and B-1 and B-2 （b）

Fig.6 Infrared transmittance of A-2 and A-3 （a） and B-1 and B-2 （b）

Fig.7 SEM images of flat interface A-2 （a） and stepped interface A-3（b）

Fig.8 SEM images of flat interface B-1 （a） and stepped interface B-2 （b）

Table 3 Average distance of growth steps on surfaces of A-2，A-3，B-1 and B-2

Sample ID	Flat interface A-2	Stepped interface A-3	Flat interface B-1	Stepped interface B-2
Average distance/μm	7.60	2.26	3.59	1.63

Fig.9 Bubble sizes and distributions of three groups under microscope on flat interface A-2

Fig.10 Bubble sizes and distributions of three groups under microscope on stepped interface A-3

Fig.11 Bubble sizes and distributions of three groups under microscope on flat interface B-1

Fig.12 Bubble sizes and distributions of three groups under microscope on stepped interface B-2

Table 4 Average bubble size，Raman FWHM and XRD FWHM of samples

Sample ID	Average bubble size/μm	Raman FWHM/cm^-1	XRD FWHM/（″）
Flat interface A-2	68.04×55.70	3.71	100.8
Stepped interface A-3	42.98×37.27	3.38	68.4
Flat interface B-1	52.03×36.89	3.48	90.0
Stepped interface B-2	37.90×35.23	3.09	46.8

Fig.13 O1s energy level spectra of flat interface A-2 （a） and stepped interface B-2 （b）

Table 5 O1s test results of flat interface A-2 and stepped interface B-2

Sample ID	［V_O］/%	［Olatt］/%	Raman FWHM/cm^-1
Flat interface A-2	40.79	59.21	3.71
Stepped interface B-2	34.55	65.45	3.09

Fig.14 Diffraction patterns of stepped interface （a） and flat interface （b）

References 29

[1]	杜　鹃，吴绍华，康　杰，等. 蓝宝石晶体材料的光电应用［J］. 红外技术，2025，47（1）：10-18.
	DU J，WU S H，KANG J，et al. Optoelectronic applications of sapphire crystal material［J］. Infrared Technology，2025，47（1）：10-18 （in Chinese）.
[2]	YANG G J，PENG Z Y，WANG Y Z，et al. Numerical study of thermal shock on infrared windows and their composites with diamond coatings under harsh conditions［J］. Diamond and Related Materials，2023，137：110117.
[3]	吴绍华，李常成，夏丽昆，等. 蓝宝石晶体材料的光电应用及发展趋势［J］. 云光技术，2012，44（2）：1-7+36.
	WU S H，LI C C，XIA L K，et al. Optoelectronic applications and development trends of sapphire crystal materials［J］. Infrared and Laser Engineering，2012，44（2）：1-7+36 （in Chinese）.
[4]	聂　辉，陆炳哲. 蓝宝石及其在军用光电设备上的应用［J］. 舰船电子工程，2005，25（2）：131-133+142.
	NIE H，LU B Z. Sapphire window and it’s application in military electro-optical equipment［J］. Ship Electronic Engineering，2005，25（2）：131-133+142 （in Chinese）.
[5]	王东海，李东振，徐　军. 导模法生长大尺寸蓝宝石板材技术取得重要突破［J］. 无机材料学报，2023，38（3）：366-367.
	WANG D H，LI D Z，XU J. An important breakthrough in the technology of sapphire plate with large size grown by the edge-defined film-fed growth method［J］. Journal of Inorganic Materials，2023，38（3）：366-367 （in Chinese）.
[6]	王东海，徐　军，李东振，等. 导模法生长超大尺寸蓝宝石板材的研究［J］. 人工晶体学报，2020，49（3）：398-401.
	WANG D H，XU J，LI D Z，et al. Study on the growth of super large sapphire plate by EFG method［J］. Journal of Synthetic Crystals，2020，49（3）：398-401 （in Chinese）.
[7]	王　铎. 大直径蓝宝石生长工艺及性能研究［D］. 长春：长春理工大学，2009.
	WANG D. Large-diameter sapphire growth process and properties［D］. Changchun：Changchun University of Science and Technology，2009 （in Chinese）.
[8]	SCHMID F，ROGERS H H，KHATTAK C P，et al. Growth of very large sapphire crystals for optical applications［J］. Inorganic Optical Materials，1998，3424：37-46.
[9]	ANTONOV P I，KURLOV V N. New advances and developments in the Stepanov method for the growth of shaped crystals［J］. Crystallography Reports，2002，47（supplement 1）：S43-S52.
[10]	杨新波，李红军，徐　军，等. 导模法生长晶体研究进展［J］. 硅酸盐学报，2008，36（增刊1）：222-227.
	YANG X B，LI H J，XU J，et al. Research progress of edge-defined film-fed crystal growth method［J］. Journal of the Chinese Ceramic Society，2008，36（supplement 1）：222-227 （in Chinese）.
[11]	于海欧，李红军，徐　军，等. 导模法生长蓝宝石晶体的退火工艺［J］. 硅酸盐学报，2012，40（6）：905-909.
	YU H O，LI H J，XU J，et al. Annealing process of sapphire crystal grown by edge defined film fed growth method［J］. Journal of the Chinese Ceramic Society，2012，40（6）：905-909 （in Chinese）.
[12]	曹稳政，何珊珊，腾亚君，等. 不同方法合成蓝宝石与天然蓝宝石的谱学对比研究［J］. 光散射学报，2022，34（4）：290-295.
	CAO W Z，HE S S，TENG Y J，et al. Comparative study on spectroscopic characteristics of natural sapphire and synthetic sapphire by different methods［J］. The Journal of Light Scattering，2022，34（4）：290-295 （in Chinese）.
[13]	SHLIMAK I，BUTENKO A，KOGAN E，et al. Irradiation-induced broadening of the Raman spectra in monolayer graphene［J］. Journal of Applied Physics，2019，126（19）：194302.
[14]	SPARAVIGNA A C. Q-Gaussians and the shapes of Raman spectral lines［J］. Physica A：Statistical Mechanics and its Applications，2023，612：1-7.
[15]	DONG X，DAI L. Transfer of Raman spectra with different resolutions applying convolution with Gaussian function［J］. Asian Journal of Chemistry，2012，24（10）：4257.
[16]	ROSSOLENKO S N. Menisci masses and weights in stepanov （EFG） technique：ribbon，rod，tube［J］. Journal of Crystal Growth，2001，231（1/2）：306-315.
[17]	宁永功，姬　洪，王志红，等. XRD摇摆曲线在单晶基片质量检测中的应用［J］. 现代仪器，1999，5（4）：34-37.
	NING Y G，JI H，WANG Z H，et al. Application of XRD rocking curve to evaluate the quality on single crystal substrates of film growing［J］. Modern Instruments，1999，5（4）：34-37 （in Chinese）.
[18]	陈伟超，罗　平，王庆国，等. 多片导模法蓝宝石晶体的缺陷研究［J］. 人工晶体学报，2021，50（4）：741-746+756.
	CHEN W C，LUO P，WANG Q G，et al. Defects of multi-plate sapphire grown from EFG technique［J］. Journal of Synthetic Crystals，2021，50（4）：741-746+756 （in Chinese）.
[19]	张晗宇，崔　云，孙　勇，等. 环境适应性中红外宽带减反射元件的研制［J］. 中国激光，2020，47（3）：56-61.
	ZHANG H Y，CUI Y，SUN Y，et al. Fabrication of environmentally adaptive mid-infrared broadband antireflection components［J］. Chinese Journal of Lasers，2020，47（3）：56-61 （in Chinese）.
[20]	WANG R X，ZHANG Q L，YANG M L，et al. Transport of bubbles at the melt/crystal interface during YAG crystal growth［J］. Optical Materials，2026，169：117498.
[21]	王东阳，贺　威，李　玲，等. 光学质量大尺寸蓝宝石单晶工艺研究［J］. 深圳大学学报（理工版），2015，32（4）：350-356.
	WANG D Y，HE W，LI L，et al. Growth technique of optical quality large-size single-crystal sapphire［J］. Journal of Shenzhen University （Science and Engineering），2015，32（4）：350-356 （in Chinese）.
[22]	蔡　迅，黎建明，刘春雷，等. 改进热交换法生长蓝宝石晶体的气泡研究［J］. 人工晶体学报，2012，41（1）：42-46.
	CAI X，LI J M，LIU C L，et al. Research on bubbles in sapphire crystal grown by modified HEM［J］. Journal of Synthetic Crystals，2012，41（1）：42-46 （in Chinese）.
[23]	姚　泰，韩杰才，左洪波，等. 蓝宝石单晶的气孔形成研究［J］. 无机材料学报，2008，23（3）：439-442.
	YAO T，HAN J C，ZUO H B，et al. Bubble formation in sapphire single crystals［J］. Journal of Inorganic Materials，2008，23（3）：439-442 （in Chinese）.
[24]	马胜利，井晓天，孙巧艳. 导模法生长白宝石单晶中的缺陷观察［J］. 无机材料学报，1998，13（1）：91-94.
	MA S L，JING X T，SUN Q Y. Observation on defects in sapphire single crystal grown by the EFG method［J］. Journal of Inorganic Materials，1998，13（1）：91-94 （in Chinese）.
[25]	王崇鲁，张　苏. 导模法生长的白宝石片状晶体中气孔的形成与消除［J］. 硅酸盐通报，1990，9（6）：41-44.
	WANG C L，ZHANG S. Formation and elimination of pores in sapphire flake crystals grown by guided mode method［J］. Bulletin of the Chinese Ceramic Society，1990，9（6）：41-44 （in Chinese）.
[26]	薛小飞. 导模法蓝宝石晶体生长热系统分析研究［D］. 西安：西安理工大学，2015.
	XUE X F. Thermal system analysis of sapphire crystal growth by the EFG method［D］. Xi'an：Xi'an University of Technology，2015 （in Chinese）.
[27]	吴小凤. 导模法生长蓝宝石晶体工艺及性能研究［D］. 南京：南京航空航天大学，2015.
	WU X F. Process and performance study of sapphire crystals grown by the EFG method［D］. Nanjing：Nanjing University of Aeronautics and Astronautics，2015 （in Chinese）.
[28]	OU G，XU Y S，WEN B，et al. Tuning defects in oxides at room temperature by lithium reduction［J］. Nature Communications，2018，9（1）：1302.
[29]	WANG J P，LIU Y，MI J X，et al. Activation of surface lattice oxygen over nanosheet LaFeO₃ with La vacancy for boosting catalysis and energy conversion［J］. Small，2025，21（31）：e2502049.