跨尺度单晶氧化镓磨损机理研究与分析

氧化镓（β-Ga2O3）是一种具有超宽禁带透明导电氧化物，具有良好的机械性 能且能实现低成本生长，在大功率电力电子器件领域有广阔发展前景。体相法生 长得到的氧化镓需经过一系列机械加工过程，才能满足功率器件晶面质量要求，而 氧化镓的硬脆难加工特性使得这一加工过程具有挑战性。本文研究了宏观层面材 料摩擦行为与湿度以及各向异性的影响，并基于纳米压痕、划痕测试与分子动力 学模拟相结合的方法在微观尺度上进一步分析了氧化镓的各向异性去除机理。本 文主要研究内容与结论如下： 在不同相对湿度环境下对 β-Ga2O3（100）晶面进行摩擦测试，分析各环境对 氧化镓材料形变与去除方式以及摩擦化学机制的影响，得到摩擦系数大小及其波 动情况随着湿度升高先增后减，5%RH 下摩擦化学反应减少，磨损率远低于湿润 环境，划痕存在磨损槽和犁沟。30%RH 与 65%RH 下磨损率差距很小，划痕存在 堆积的粉末状颗粒，65%RH 下存在层状裂纹。磨损的主要机制在干燥环境下为机 械磨损与粘着磨损，湿润环境下为摩擦化学磨损与沟槽磨损。 对单晶 β-Ga2O3 的（201），（100），（010），（001）四个晶面进行摩擦磨损测 试，探讨各向异性在摩擦行为及材料去除上的表现形式，得到各晶面上两个相互 垂直的晶向磨损率相差 1~2 个数量级，（001）晶面上相差最大，且在大部分晶面 上 [010] 向均不耐磨。解理面（001）晶面 [010] 晶向划痕内部出现块状剥落及方向 与划痕方向相同的层状裂纹，[100] 晶向划痕中部存在大量可能起润滑作用的粉末 状成分。 通过纳米压痕与划痕测试，并结合分子动力学模拟，在单晶 β-Ga2O3 的 （100）、（010）和（201）三个晶面研究其微观尺度上的各向异性去除行为，由 纳米压痕得到（100）晶面具有最低硬度值，适宜作为加工面，（201）晶面硬度值 最高。分析纳米划痕过程得到在渐进载荷作用下氧化镓变形与去除方式存在弹性、 塑性、脆性的演变，（201）面包容各晶向的塑性区间最小，（100）面各晶向塑性区 间重合度高且区域广，表面易实现光滑去除。由分子动力学模拟，得到（201）面 [010] 向切向力在模拟与实际中变化趋势不同，说明该晶向受真实环境影响最大。

Gallium oxide (β-Ga2O3) is a transparent conductive oxide with an ultra-wide bandgap. It has good mechanical properties and can be grown at low cost. It has broad development prospects in the field of high-power electronic devices. The gallium oxide grown by the bulk method needs to go through a series of mechanical processing processes to meet the crystal plane quality requirements of power devices, and the hard, brittle and difficult-to-process characteristics of gallium oxide make this processing process challenging. In this paper, the influence of material friction behavior, humidity and anisotropy on the macroscopic level is studied, and the anisotropic removal mechanism of gallium oxide is further analyzed on the microscopic scale based on the combination of nanoindentation, scratch testing and molecular dynamics simulation. The main research contents and conclusions of this paper are as follows: Conduct friction tests on β-Ga2O3 (100) crystal planes under different relative humidity environments, analyze the effects of various environments on the deformation and removal methods of gallium oxide materials and the tribochemical mechanism, and obtain the friction coefficient and its The fluctuations first increased and then decreased with the increase of humidity, the tribochemical reaction decreased in a dry environment, and a water film was formed on the surface of the sample in a high humidity environment. The wear rate in a dry environment is much lower than that in a wet environment, and the difference between the wear rate at 30%RH and 65%RH is very small. The main mechanism of wear is mechanical wear in a dry environment, and tribochemical wear in a wet environment. Conduct friction and wear tests on (201), (100), (010), (001) four crystal planes of single crystal β-Ga2O3 to explore the manifestation of anisotropy in friction behavior and material removal, It is obtained that the wear rates of the two perpendicular crystal directions on each crystal plane differ by 1 to 2 orders of magnitude, and the (001) crystal plane has the largest difference, and the [010] direction on most crystal planes is not wear resistant. On the cleavage plane (001) crystal plane [010] crystal direction scratches appear massive exfoliation and layered cracks with the same direction as the scratch direction, and in the middle of [100] crystal direction scratches there are a large amount of powder components that may play a lubricating role. Through nano-indentation and nano-scratch tests, combined with molecular dynamics simulation, the three crystal planes (100), (010) and (201) of single crystal β-Ga2O3 are studied on the microscopic scale. According to the anisotropic removal behavior, the (100) crystal plane obtained by nanoindentation has the lowest hardness value, which is suitable for processing, and the (201) crystal plane has the highest hardness value. By analyzing the nano-scratch process, it is found that the deformation and removal of gallium oxide have the evolution of elasticity, plasticity, and brittleness under the action of progressive load. The (201) plane contains the smallest plastic interval of each crystal orientation, and the coincidence degree of the plastic interval of each crystal orientation on the (100) plane High and wide area, the surface is easy to achieve smooth removal. From the molecular dynamics simulation, it is obtained that the tangential force of the (201) plane [010] has different trends in simulation and reality, indicating that the crystal orientation is most affected by the real environment.

[1] REESE S B, REMO T, GREEN J, et al. How much will gallium oxide power electronics cost?[J]. Joule, 2019, 3(4): 903-907.
[2] PEARTON S, YANG J, CARY IV P H, et al. A review of Ga2O3 materials, processing, and devices[J]. Applied Physics Reviews, 2018, 5(1): 011301.
[3] 王新月, 张胜男, 霍晓青, 等. 超宽禁带半导体 𝛽-Ga2O3 相关研究进展[J]. 人工晶体学报,2021, 50(11): 1995-2012.
[4] HIGASHIWAKI M, SASAKI K, MURAKAMI H, et al. Recent progress in Ga2O3 power de vices[J]. Semiconductor Science and Technology, 2016, 31(3): 034001.
[5] GELLER S. Crystal structure of 𝛽-Ga2O3 [J]. The Journal of Chemical Physics, 1960, 33(3):676-684.
[6] YU J, WANG Y, LI H, et al. Tailoring the solar-blind photoresponse characteristics of 𝛽-Ga2O3epitaxial films through lattice mismatch and crystal orientation[J]. Journal of Physics D: AppliedPhysics, 2020, 53(24): 24LT01.
[7] WANG X, XU Q, FAN F, et al. Study of the Phase Transformation of Single Particles of Ga2O3by UV-Raman Spectroscopy and High-Resolution TEM[J]. Chemistry–An Asian Journal, 2013,8(9): 2189-2195.
[8] BAE J, KIM H W, KANG I H, et al. High breakdown voltage quasi-two-dimensional 𝛽-Ga2O3field-effect transistors with a boron nitride field plate[J]. Applied Physics Letters, 2018, 112(12): 122102.
[9] OSHIMA T, HASHIGUCHI A, MORIBAYASHI T, et al. Electrical properties of Schottkybarrier diodes fabricated on (001) 𝛽-Ga2O3substrates with crystal defects[J]. Japanese Journalof Applied Physics, 2017, 56(8): 086501.
[10] BIN ANOOZ S, GRÜNEBERG R, WOUTERS C, et al. Step flow growth of 𝛽-Ga2O3thin filmson vicinal (100) 𝛽-Ga2O3substrates grown by MOVPE[J]. Applied Physics Letters, 2020, 116(18): 182106.
[11] MUHAMMED M, ROLDAN M, YAMASHITA Y, et al. High-quality III-nitride films on con ductive, transparent (201)-oriented 𝛽-Ga2O3 using a GaN buffer layer[J]. Scientific reports,2016, 6(1): 29747.
[12] MA J, ZHENG M, CHEN C, et al. Efficient and stable nonfullerene-graded heterojunction inverted perovskite solar cells with inorganic Ga2O3tunneling protective nanolayer[J]. AdvancedFunctional Materials, 2018, 28(41): 1804128.
[13] XUE H, HE Q, JIAN G, et al. An overview of the ultrawide bandgap Ga2O3semiconductor-based Schottky barrier diode for power electronics application[J]. Nanoscale research letters, 2018, 13(1): 1-13.
[14] AHMADI E, OSHIMA Y. Materials issues and devices of 𝛼-and 𝛽-Ga2O3[J]. Journal of Applied Physics, 2019, 126(16): 160901.
[15] GALAZKA Z, UECKER R, KLIMM D, et al. Scaling-up of bulk 𝛽-Ga2O3single crystals bythe Czochralski method[J]. ECS Journal of Solid State Science and Technology, 2016, 6(2):Q3007.
[16] TOMM Y, KO J, YOSHIKAWA A, et al. Floating zone growth of 𝛽-Ga2O3: a new windowmaterial for optoelectronic device applications[J]. Solar energy materials and solar cells, 2001,66(1-4): 369-374.
[17] KURAMATA A, KOSHI K, WATANABE S, et al. High-quality 𝛽-Ga2O3single crystalsgrown by edge-defined film-fed growth[J]. Japanese Journal of Applied Physics, 2016, 55(12):1202A2.
[18] BALDINI M, ALBRECHT M, FIEDLER A, et al. Si-and Sn-doped homoepitaxial 𝛽-Ga2O3layers grown by MOVPE on (010)-oriented substrates[J]. ECS Journal of Solid State Scienceand Technology, 2016, 6(2): Q3040.
[19] MAZZOLINI P, FALKENSTEIN A, WOUTERS C, et al. Substrate-orientation dependence of𝛽-Ga2O3(100),(010),(001), and (201) homoepitaxy by indium-mediated metal-exchange cat alyzed molecular beam epitaxy (MEXCAT-MBE)[J]. Apl Materials, 2020, 8(1): 011107.
[20] NOMURA K, GOTO K, TOGASHI R, et al. Thermodynamic study of 𝛽-Ga2O3 growth byhalide vapor phase epitaxy[J]. Journal of Crystal Growth, 2014, 405: 19-22.
[21] LEE S D, KANEKO K, FUJITA S. Homoepitaxial growth of beta gallium oxide films by mistchemical vapor deposition[J]. Japanese Journal of Applied Physics, 2016, 55(12): 1202B8.
[22] KURAMATA A, KOSHI K, WATANABE S, et al. Bulk crystal growth of Ga2O3[C]//Oxide based Materials and Devices IX: volume 10533. SPIE, 2018: 9-14.
[23] LI G, XIAO C, ZHANG S, et al. An experimental investigation of silicon wafer thinning bysequentially using constant-pressure diamond grinding and fixed-abrasive chemical mechanicalpolishing[J]. Journal of Materials Processing Technology, 2022, 301: 117453.
[24] VAN ERP R, SOLEIMANZADEH R, NELA L, et al. Co-designing electronics with microflu idics for more sustainable cooling[J]. Nature, 2020, 585(7824): 211-216.
[25] XU W, WANG Y, YOU T, et al. First demonstration of waferscale heterogeneous integration ofGa2O3 MOSFETs on SiC and Si substrates by ion-cutting process[C]//2019 IEEE InternationalElectron Devices Meeting (IEDM). IEEE, 2019: 12-5.
[26] KIM Y S, MAEDA N, KITADA H, et al. Advanced wafer thinning technology and feasibilitytest for 3D integration[J]. Microelectronic Engineering, 2013, 107: 65-71.
[27] MA X, XU R, XU J, et al. In-plane crystalline anisotropy of bulk 𝛽-Ga2O3[J]. Journal ofApplied Crystallography, 2021, 54(4): 1153-1157.
[28] JANG S, JUNG S, BEERS K, et al. A comparative study of wet etching and contacts on (201)and (010) oriented 𝛽-Ga2O3[J]. Journal of Alloys and Compounds, 2018, 731: 118-125.
[29] JOCHUM W, PENNER S, FÖTTINGER K, et al. Hydrogen on polycrystalline 𝛽-Ga2O3: Sur face chemisorption, defect formation, and reactivity[J]. Journal of Catalysis, 2008, 256(2):268-277.
[30] AIDA H, TAKEDA H, KOYAMA K, et al. Chemical mechanical polishing of gallium nitridewith colloidal silica[J]. Journal of The Electrochemical Society, 2011, 158(12): H1206.
[31] KIDO T, NAGAYA M, KAWATA K, et al. A novel grinding technique for 4H-SiC single-crystalwafers using tribo-catalytic abrasives[C]//Materials Science Forum: volume 778. Trans TechPubl, 2014: 754-758.
[32] ZENG G, TAN C K, TANSU N, et al. Ultralow wear of gallium nitride[J]. Applied PhysicsLetters, 2016, 109(5): 051602.
[33] YAMAGUCHI H, WATANABE S, YAMAOKA Y, et al. Subsurface-damaged layer in (010)-oriented 𝛽-Ga2O3substrates[J]. Japanese Journal of Applied Physics, 2020, 59(12): 125503.
[34] BUTENKO P, GUZILOVA L, CHIKIRYAKA A, et al. Wear resistance of 𝛼-and 𝛽-galliumoxide coatings[J]. Materials Physics and Mechanics, 2021, 47(1): 52-58.
[35] BUTENKO P, GUZILOVA L, CHIKIRYAKA A, et al. Impact on the subsurface layers of thesingle-crystal 𝛽-Ga2O3 wafers induced by a mechanical wear[J]. Materials Science in Semi conductor Processing, 2022, 143: 106520.
[36] CHEN L, HU L, XIAO C, et al. Effect of crystallographic orientation on mechanical removalof CaF2[J]. Wear, 2017, 376: 409-416.
[37] XIAO C, DENG C, ZHANG P, et al. Interplay between solution chemistry and mechanical acti vation in friction-induced material removal of silicon surface in aqueous solution[J]. TribologyInternational, 2020, 148: 106319.
[38] HUANG C, MU W, ZHOU H, et al. Effect of OH- on chemical mechanical polishing of 𝛽-Ga2O3(100) substrate using an alkaline slurry[J]. RSC advances, 2018, 8(12): 6544-6550.
[39] GAO S, WU Y, KANG R, et al. Nanogrinding induced surface and deformation mechanism ofsingle crystal 𝛽-Ga2O3[J]. Materials Science in Semiconductor Processing, 2018, 79: 165-170.
[40] IMOTO R, STEVENS F, LANGFORD S, et al. Atomic force microscopy studies of chemical–mechanical processes on silicon (100) surfaces[J]. Applied Physics A, 2009, 94: 35-43.
[41] XIAO C, XIN X, HE X, et al. Surface structure dependence of mechanochemical etching:Scanning probe-based nanolithography study on Si (100), Si (110), and Si (111)[J]. ACS appliedmaterials & interfaces, 2019, 11(23): 20583-20588.
[42] XIAO C, CHEN C, WANG H, et al. Effect of counter-surface chemistry on defect-free materialremoval of monocrystalline silicon[J]. Wear, 2019, 426: 1233-1239.
[43] XIAO C, GUO J, ZHANG P, et al. Effect of crystal plane orientation on tribochemical removalof monocrystalline silicon[J]. Scientific Reports, 2017, 7(1): 40750.
[44] ZHANG Y, ZHANG L, LIU M, et al. Understanding the friction and wear of KDP crystals bynanoscratching[J]. Wear, 2015, 332: 900-906.
[45] 高尚, 李洪钢, 康仁科, 等. 新一代半导体材料氧化镓单晶的制备方法及其超精密加工技术研究进展[J]. 机械工程学报, 2021, 57(9): 213-232.
[46] 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.
[47] SHIMAMURA K, VILLORA E, MURAMATU K, et al. Optoelectronic single-crystal candi dates for UV/VUV light sources (< Special Issue> Crystal Growth Technology of Fluoride andOxide Developed from the Viewpoint of Their Material and Functional Properties)[J]. J. Jpn.Assoc. Cryst. Growth, 2006, 33: 147-154.
[48] AIDA H, NISHIGUCHI K, TAKEDA H, et al. Growth of 𝛽-Ga2O3single crystals by the edge defined, film fed growth method[J]. Japanese Journal of Applied Physics, 2008, 47(11R): 8506.
[49] 穆文祥, 贾志泰, 陶绪堂, 等. 4 英寸氧化镓单晶生长与性能[J]. Journal of Synthetic Crystals,2022, 51(9-10): 1749-1753.
[50] 唐慧丽, 何诺天, 罗平, 等. 超宽禁带半导体 𝛽-Ga2O3 单晶生长突破 2 英寸[J]. 人工晶体学报, 2017, 46(12): 2533-2534.
[51] 张颖武, 练小正, 张政, 等. 低缺陷 𝛽-Ga2O3 单晶材料生长技术研究[J]. 河南科技, 2016(13): 140-142.
[52] CHI Z, ASHER J J, JENNINGS M R, et al. Ga2O3 and Related Ultra-Wide Bandgap PowerSemiconductor Oxides: New Energy Electronics Solutions for CO2 Emission Mitigation[J].Materials, 2022, 15(3): 1164.
[53] WEN S, HUANG P. Principles of tribology[M]. John Wiley & Sons, 2012.
[54] SCHUH C A. Nanoindentation studies of materials[J]. Materials today, 2006, 9(5): 32-40.
[55] TANG G. Indentation analysis and mechanical modeling of multilayered composites[Z]. 2009.
[56] DATTA D, RAI H, SINGH S, et al. Nanoscale tribological aspects of chemical mechanicalpolishing: A review[J]. Applied Surface Science Advances, 2022, 11: 100286.
[57] BEAKE B, HARRIS A, LISKIEWICZ T. Review of recent progress in nanoscratch testing[J].Tribology-Materials, Surfaces & Interfaces, 2013, 7(2): 87-96.
[58] MOHAMMED A, ABDULLAH A. Scanning electron microscopy (SEM): A review[C]//Proceedings of the 2018 International Conference on Hydraulics and Pneumatics—HERVEX,Băile Govora, Romania: volume 2018. 2018: 7-9.
[59] ALI A S. Application of nanomaterials in environmental improvement[J]. Nanotechnology andthe Environment, 2020.
[60] RAPAPORT D C, RAPAPORT D C R. The art of molecular dynamics simulation[M]. Cam bridge university press, 2004.
[61] SRIVASTAVA I, KOTIA A, GHOSH S K, et al. Recent advances of molecular dynamics sim ulations in nanotribology[J]. Journal of Molecular Liquids, 2021, 335: 116154.
[62] ZENG G, TANSU N, KRICK B A. Moisture dependent wear mechanisms of gallium nitride[J]. Tribology International, 2018, 118: 120-127.
[63] VÍLLORA E G, ARJOCA S, SHIMAMURA K, et al. 𝛽-Ga2O3 and single-crystal phosphorsfor high-brightness white LEDs and LDs, and [beta]-Ga2O3 potential for next generation ofpower devices[C]//Oxide-based Materials and Devices V: volume 8987. SPIE, 2014: 371-382.
[64] YAMAGUCHI H, KURAMATA A. Stacking faults in 𝛽-Ga2O3 crystals observed by X-raytopography[J]. Journal of Applied Crystallography, 2018, 51(5): 1372-1377.
[65] LU S, ZHANG B, LI X, et al. Grain boundary effect on nanoindentation: A multiscale discretedislocation dynamics model[J]. Journal of the Mechanics and Physics of Solids, 2019, 126:117-135.