近化学计量比铌酸锂晶体的孪晶缺陷研究

doi:10.15541/jim20240343

无机材料学报 ›› 2025, Vol. 40 ›› Issue (2): 196-204.DOI: 10.15541/jim20240343 CSTR: 32189.14.10.15541/jim20240343

近化学计量比铌酸锂晶体的孪晶缺陷研究

郝永鑫¹^,²(), 孙军³(), 杨金凤³, 赵晨成¹^,², 刘子琦¹^,², 李清连¹^,², 许京军¹

1.南开大学物理科学学院, 天津 300071
2.山西大学极端光学协同创新中心, 太原 030006
3.中国科学院新疆理化技术研究所, 晶体材料研究中心, 新疆功能晶体材料重点实验室, 乌鲁木齐 830011

收稿日期:2024-07-19 修回日期:2024-09-02 出版日期:2025-02-20 网络出版日期:2024-11-15
通讯作者: 孙军, 研究员. E-mail: sunjun@nankai.edu.cn
作者简介:郝永鑫(1997-), 女, 博士研究生. E-mail: bigcrystal@mail.nankai.edu.cn
基金资助:
国家自然科学基金(61575099);高等学校学科创新引智计划(111计划);高等学校学科创新引智计划(B23045)

Twinning Defects in Near-stoichiometric Lithium Niobate Single Crystals

HAO Yongxin¹^,²(), SUN Jun³(), YANG Jinfeng³, ZHAO Chencheng¹^,², LIU Ziqi¹^,², LI Qinglian¹^,², XU Jingjun¹

1. School of Physics, Nankai University, Tianjin 300071, China
2. Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
3. Research Center for Crystal Materials, Xinjiang Key Laboratory of Functional Crystal Materials, Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Urumqi 830011, China

Received:2024-07-19 Revised:2024-09-02 Published:2025-02-20 Online:2024-11-15
Contact: SUN Jun, professor. E-mail: sunjun@nankai.edu.cn
About author:HAO Yongxin (1997-), female, PhD candidate. E-mail: bigcrystal@mail.nankai.edu.cn
Supported by:
National Natural Science Foundation of China(61575099);Program of Introducing Talents of Discipline to Universities(111 Project);Program of Introducing Talents of Discipline to Universities(B23045)

摘要/Abstract

摘要：

铌酸锂(LiNbO₃, 简称LN)晶体因其优良的非线性、电光等效应成为最具应用价值的集成光子学材料之一。与同成分铌酸锂(Congruent Lithium Niobate, CLN)晶体相比, 近化学计量比铌酸锂(Near-stoichiometric Lithium Niobate, nSLN)晶体的非线性、电光等性能更加突出, 具有更高的应用价值。利用扩散法能够制备组分均匀的实用化nSLN晶体, 然而对大尺寸LN晶体进行扩散处理时, 极易产生孪晶并导致晶片开裂。针对上述问题, 本工作开展了扩散法制备大尺寸nSLN晶体的研究, 对扩散后晶片上的孪晶缺陷进行表征, 分析了孪晶的产生机制, 并通过改进晶片放置方式制备了完整的4英寸(100 nm)和6英寸(153 nm)晶片, 最后测试了晶片的组分和透过率。结果表明, 晶片组分均不低于49.94%(摩尔分数), 接近化学计量比, 其透过率在600~3300 nm范围内均高于71%。扩散法制备的Z-cut和X-cut晶片上均出现了孪晶, 同时Z-cut晶片上的孪晶两两相交时产生裂纹, 而X-cut晶片上并未出现裂纹。分析表明Z-cut和X-cut晶片孪晶面为 ${01 1 ¯ 2}$ , 该孪晶属于形变孪晶。根据形变孪晶的产生机制, 认为富锂原料不均匀形变是产生孪晶的主要驱动力。最终, 通过改进扩散处理工艺, 抑制了扩散孪晶的产生, 提高了4英寸(100 nm)、6英寸(153 nm)nSLN晶片的成品率。

关键词: 近化学计量比铌酸锂, 扩散法, 孪晶, 富锂气氛

Abstract:

Lithium niobate (LN) single crystals have emerged as one of the most valuable materials for integrated photonics materials due to their exceptional properties, including non-linear and electro-optical effects. Compared to congruent lithium niobate (CLN) crystals, near-stoichiometric lithium niobate (nSLN) crystals exhibit more pronounced non-linear and electro-optical properties, offering higher application value. nSLN crystals with high compositional uniformity can be prepared using a vapor transport equilibration method. However, large-size LN single crystals are highly susceptible to twinning defects and wafer cracks during diffusion processing. Here, large size nSLN single crystals were prepared using the vapor transport equilibration method to address the aforementioned defects and cracking. The twinning defects within wafers after diffusion processing were characterized, the mechanisms of twinning formation were analyzed, the wafer placement method to produce complete 4-inch (100 nm) and 6-inch (153 nm) wafers was modified, and the composition and transmittance of wafers were tested. Results indicate that composition of the wafers is at least 49.94% (in mole), approaching stoichiometric ratio, and their transmittance is greater than 71% across the 600-3300 nm range. Both Z-cut and X-cut wafers prepared by vapor transport equilibration method exhibited twinning defects. However, cracks were observed when twinning defects intersected on Z-cut wafers, whereas no cracks were present on X-cut wafers. The twinning planes on both Z-cut and X-cut wafers were depending on ${01 1 ¯ 2}$ , which they were identified as deformation twins. According to the mechanism of deformation twin formation, the non-uniform deformation of lithium-rich materials is identified as the primary driving force beneath the twin formation. Ultimately, it was proposed to mitigate twin activation by modifying the diffusion treatment process, thereby increasing the yields of 4-inch (100 nm) and 6-inch (153 nm) nSLN wafers.

Key words: near-stoichiometric lithium niobate, vapor transport equilibration, twinning defect, Li-rich atmosphere

中图分类号:

O782

郝永鑫, 孙军, 杨金凤, 赵晨成, 刘子琦, 李清连, 许京军. 近化学计量比铌酸锂晶体的孪晶缺陷研究[J]. 无机材料学报, 2025, 40(2): 196-204.

HAO Yongxin, SUN Jun, YANG Jinfeng, ZHAO Chencheng, LIU Ziqi, LI Qinglian, XU Jingjun. Twinning Defects in Near-stoichiometric Lithium Niobate Single Crystals[J]. Journal of Inorganic Materials, 2025, 40(2): 196-204.

图/表 14

图1 晶片锂含量测试所用样品位置示意图

Fig. 1 Schematic diagram of sample locations for wafer Li content testing

表1 不同扩散条件下晶体扩散结果

Table 1 Results of crystals diffusion under different conditions

Experiment	Sample	Crystal		Diffusion treatment condition			Results
Experiment	Sample	Orientation	Size/mm	Temperature/℃	Time/h	Wafer placement	Results
1	VTE-1-1	Z-cut	ϕ100×0.86	1100	120	Horizontal	Cracked, twins
1	VTE-1-2	Z-cut	ϕ100×0.86	1100	120	Horizontal	Cracked, twins
2	VTE-2-1	Z-cut	ϕ100×0.86	1100	120	Vertical	Uncracked, twins
2	VTE-2-2	Z-cut	ϕ100×0.86	1100	120	Vertical	Uncracked, twins
3	VTE-3-Z	Z-cut	ϕ100×1.02	1100	300	Vertical	Uncracked, twins
3	VTE-3-X	X-cut	ϕ76.2×0.50	1100	300	Vertical	Uncracked, twins
4	VTE-4-1	Z-cut	ϕ100×0.86	1100	120	Vertical	Uncracked, twins
4	VTE-4-2	Z-cut	ϕ100×0.86	1100	120	Vertical	Uncracked, twins
5	VTE-5-1	Z-cut	ϕ100×0.86	1100	120	Vertical	Uncracked, twins
5	VTE-5-2	Z-cut	ϕ100×0.86	1100	120	Vertical	Uncracked, without twins
6	VTE-6-1	Z-cut	ϕ100×0.86	1100	120	Horizontal	Uncracked, without twins
6	VTE-6-2	Z-cut	ϕ100×0.86	1100	120	Horizontal	Uncracked, without twins
7	VTE-7	Z-cut	ϕ153×1.02	1100	120	Horizontal	Uncracked, without twins

图2 第1~6次扩散实验得到的4英寸(100 nm)Z-cut LN晶片

Fig. 2 4-inch (100 nm) Z-cut LN wafers obtained from VTE experiments 1-6 (a) VTE-1-1; (b) VTE-1-2; (c) VTE-2-1; (d) VTE-2-2; (e) VTE-3-Z; (f) VTE-3-X; (g) VTE-4-1; (h) VTE-4-2; (i) VTE-5-1; (j) VTE-5-2; (k) VTE-6-1; (l) VTE-6-2

图3 第4次扩散实验装置示意图

Fig. 3 Schematic diagram of experimental device for the 4th VTE experiment

图4 第7次扩散实验得到的6英寸(153 nm)Z-cut nSLN晶片(VTE-7)

Fig. 4 6-inch (153 nm) Z-cut nSLN wafer obtained from the 7th VTE experiment (VTE-7)

表2 不同晶片的居里温度TC和锂含量CLi

Table 2 Curie temperatures (TC) and Li contents (CLi) of different wafers

Sample		T_C/℃	Average of T_C/℃	C_Li/% (in mole)
VTE-5-2	1	1200	1200.2	49.94
	2	1201
	3	1200
	4	1201
	5	1199
VTE-6-1	1	1202	1201.6	49.98
	2	1201
	3	1202
	4	1201
	5	1202
VTE-7	1	1202	1201.0	49.96
	2	1201
	3	1200
	4	1201
	5	1201

图5 CLN晶片和nSLN晶片的透过光谱图

Fig. 5 Transmission spectra of CLN wafer and nSLN wafers (a) VTE-5-2; (b) VTE-6-1; (c) VTE-7

图6 在180°内旋转不同角度时晶片VTE-3-Z和VTE-3-X的孪晶区域双折射变化情况

Fig. 6 Birefringence changes in the twinning regions of wafers VTE-3-Z and VTE-3-X rotated at different angles within 180° (a) 0°-VTE-3-Z; (b) 45°-VTE-3-Z; (c) 90°-VTE-3-Z; (d) 135°-VTE- 3-Z; (e) 0°-VTE-3-X; (f) 45°-VTE-3-X; (g) 90°-VTE-3-X; (h) 135°-VTE- 3-X

图7 扩散处理后Z-cut晶片上孪晶条纹的方向

Fig. 7 Direction of the twinned lamella on the Z-cut wafer after VTE process (a) Wafer VTE-3-Z; (b) Schematic diagram of VTE-3-Z; (c) Angle between the twinned lamella and the Z-plane is 57°; (d) Angle between the twinned lamella and the X-plane is 90°

图8 晶片VTE-1-1中孪晶面的X射线衍射图谱

Fig. 8 X-ray diffraction pattern of the twinning plane within the wafer VTE-1-1

表3 LN晶体各晶面族与(0001)面的夹角[22]

Table 3 Angles between families of crystal planes and (0001) plane of LN crystal[22]

Family of LN crystal planes	Angle	Family of LN crystal planes	Angle
${10 1 ¯ 0}$	90°	${11 2 ¯ 0}$	90°
${10 1 ¯ 1}$	72°10′	${22 4 ¯ 3}$	74°26′
${10 1 ¯ 4}$	37°52′	${01 1 ¯ 2}$	57°15′
${11 2 ¯ 3}$	60°53′	${01 1 ¯ 8}$	21°14′
${11 2 ¯ 6}$	41°55′	${02 2 ¯ 1}$	80°52′

表3 LN晶体各晶面族与(0001)面的夹角[22]

Table 3 Angles between families of crystal planes and (0001) plane of LN crystal[22]

Family of LN crystal planes	Angle	Family of LN crystal planes	Angle
${10 1 ¯ 0}$	90°	${11 2 ¯ 0}$	90°
${10 1 ¯ 1}$	72°10′	${22 4 ¯ 3}$	74°26′
${10 1 ¯ 4}$	37°52′	${01 1 ¯ 2}$	57°15′
${11 2 ¯ 3}$	60°53′	${01 1 ¯ 8}$	21°14′
${11 2 ¯ 6}$	41°55′	${02 2 ¯ 1}$	80°52′

图9 抛光前后Z-cut 晶片上孪晶相交处的裂纹

Fig. 9 Cracks at crossing of twins on Z-cut wafers before and after polishing (a) Two twinned lamella (before polishing); (b) Three twinned lamella (before polishing); (c) Two twinned lamella (after polishing); (d) Three twinned lamella (after polishing)

图10 扩散处理后X-cut晶片上孪晶条纹的方向

Fig. 10 Direction of the twinned lamella on the X-cut wafer after VTE process (a) Wafer VTE-3-X; (b) Schematic diagram of VTE-3-X; (c) Angle between the wider twinned lamella and the Z-plane is 37°; (d) Angle between the narrower twinned lamella and the Z-plane is 57°; (e) Angle between the wider twinned lamella and the Y-axis is 30°; (f) Angle between the projection of the narrower twinned lamella and the Y-axis is 90°; (g) Projections of ( 1 1 ¯ 02 ) and ( 1 ¯ 012 ) on the X-plane; (h) Schematic diagram of observation directions ( 1 1 ¯ 02 ) and ( 1 ¯ 012 )

图11 LN晶体孪生形变时铌原子(或锂原子)的滑移

Fig. 11 Slip of niobium atoms (or lithium atoms) during twinning deformation of LN crystal

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近化学计量比铌酸锂晶体的孪晶缺陷研究

Twinning Defects in Near-stoichiometric Lithium Niobate Single Crystals

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