Effect of tool angle in nanocutting of single crystal GaN using diamond cutter
-
摘要: 为探究刀具角度对单晶氮化镓（GaN）切削诱导变形行为的影响，对金刚石纳米切削单晶GaN进行分子动力学模拟，并开展实验验证。结果表明：较大的正前角和较小的负前角可强化剪切作用，有利于切屑成形，减少原子侧向流动；而较大的负前角则会加深亚表层损伤。通过位错提取算法（DXA）和晶体结构识别算法（IDS）结合应力应变分析发现，较大的负前角和负后角可引起应力和温度升高，促进位错形核和相变，加剧非晶化。正前角和正后角切削可缓解亚表层损伤，促进去除，更有利于获得优质低损表面。Abstract:
Objectives Single-crystal gallium nitride (GaN) is a pivotal semiconductor material widely utilized in high-power, high-frequency electronic devices, and optoelectronic applications. However, its inherent hardness and brittleness pose significant challenges in achieving damage-free surfaces during ultra-precision machining. Understanding the fundamental deformation mechanisms induced by cutting, particularly the critical role of tool geometry, is essential for advancing GaN machining technology. This study aims to comprehensively elucidate the influence mechanism of diamond tool angles, specifically the rake angle and flank angle, on the cutting-induced deformation behavior and subsurface damage formation in single-crystal GaN at the nanoscale. The primary objective is to establish clear relationships between tool angles, material removal mechanisms, defect generation (dislocations, phase transformation, amorphization), and final surface integrity, thereby providing foundational knowledge for optimizing ultra-precision machining processes. Methods To achieve these objectives, a rigorous multi-scale investigation is conducted, combining molecular dynamics simulation with experimental verification. Large-scale MD simulations are meticulously performed to model the nanoscale cutting process of single-crystal GaN using a diamond tool. The simulations employed highly validates interatomic potentials capable of capturing the complex bonding and deformation behavior of GaN. The model incorporates realistic crystal orientations and environmental conditions. The influence of tool angles is systematically explored by simulating cutting processes with a wide range of rake angles (−18°, −12°, −6°, 6°, 12°, 18°) and flank angles (−18°, −12°, −6°, 6°, 12°, 18°). Post-simulation analysis utilizes sophisticated algorithms to dissect the deformation mechanisms: employed to identify, characterize, and quantify the evolution of dislocations, including their types (e.g., perfect dislocations, partial dislocations), Burgers vectors, and densities within the workpiece. Used to distinguish between the pristine wurtzite GaN structure, transformed phases (e.g., possible local zinc-blende or other metastable structures under high stress), and amorphous regions generated during cutting. Local atomic stress (Von Mises or equivalent stress) and strain distributions are calculated and visualized to correlate mechanical loading with observed deformation and damage. Atomic kinetic energy is tracked to map the temperature evolution within the cutting zone and subsurface layers. To corroborate the simulation findings, controlled nanocutting experiments are conducted on single-crystal GaN substrates. Crucially, two distinct diamond abrasive grains with differing morphologies are employed as cutting tools: rake angle of −70° and a flank angle of 10°; rake angle of −43° and a flank angle of 20°.This direct comparison allows for the experimental assessment of the impact of varying rake and flank angles on surface morphology, chip formation behavior, and subsurface damage extent, using techniques such as transmission electron microscopy (TEM) and optical microscopy for cross-sectional analysis. Results The integrated simulation and experimental approach yields profound insights into the role of tool angles: Increasing the positive rake angle or reducing the magnitude of a negative rake angle is found to significantly enhance the shear-dominated material removal mechanism. This promotes more efficient and continuous chip formation while effectively suppressing undesirable lateral atomic flow and material pile-up at the groove sides, leading to improved groove definition. Conversely, increasing the magnitude of the negative rake angle dramatically exacerbates subsurface damage. The highly compressed wedge beneath the tool tip induces severe plastic deformation deeper into the substrate. Comprehensive analysis using DXA, and stress-strain fields reveals the fundamental mechanisms triggered by large negative rake and flank angles: These tool geometries induce substantially higher compressive and shear stresses within the primary deformation zone directly ahead of the tool and the subsurface region. Consequently, localized temperatures rise significantly due to intense plastic work and friction. The extreme mechanical and thermal loading promotes prolific nucleation of dislocations. These dislocations readily propagate and interact, forming complex networks. The high von Mises stress and shear stress beneath the tool facilitate solid-state phase transformations from the stable wurtzite structure to other phases. Furthermore, the intense deformation and temperature lead to extensive amorphization (loss of long-range crystalline order) within the subsurface layer. Employing tools with positive rake angles and adequate positive flank angles demonstrably alleviates subsurface damage. The cutting mechanics shift towards efficient shearing at the primary shear zone, minimizing the crushing effect below the tool. This promotes cleaner material removal, reduces dislocation density and amorphization depth, and consequently facilitates the generation of high-quality surfaces with minimal subsurface damage. Nanocutting experiments using the two specific diamond grains provids clear validation. more negative rake consistently produced scratches with significantly greater pile-up, more pronounced lateral cracks, and deeper subsurface damage zones compared to less negative rake and larger flank angle, as evidenced by TEM characterization. This directly supports the simulation predictions regarding the detrimental effects of highly negative rake angles. Conclusions This comprehensive study, synergizing high-fidelity molecular dynamics simulations with targeted experimental validation using distinct tool geometries, has significantly deepened the understanding of the nanoscale deformation and damage mechanisms in single-crystal GaN during diamond cutting. It unequivocally establishes that: Tool rake angle is a paramount factor governing the dominant material removal mode, chip formation efficiency, and the severity of subsurface damage. Large negative rake angles, while sometimes necessary for tool edge strength, induce extreme stress and temperature conditions that promote massive dislocation activity, phase transformation, and amorphization, leading to deep subsurface damage. Positive rake angles and sufficient positive flank angles promote shear-dominated cutting, suppress deleterious lateral flow and deep damage, and are highly conducive to achieving superior surface integrity with minimal subsurface defects. The mechanistic insights gained, particularly the detailed characterization of defect evolution (dislocations, phase changes, amorphous layers) linked directly to specific tool angles, provide crucial theoretical guidance and a robust scientific foundation for the rational design and optimization of ultra-precision machining (e.g., diamond turning, grinding, polishing) processes for single-crystal GaN. This knowledge is vital for enhancing the performance and reliability of next-generation GaN-based devices. -
Key words:
- single crystal GaN /
- diamond cutter /
- nano-cutting /
- molecular dynamics /
- tool angle /
- deformation
-
图 2 单颗粒金刚石切削示意图及实验装置
Figure 2. Schematic illustrating single grit cutting and corresponding experimental setup
图 3 刀具金刚石颗粒显微形貌及截面轮廓
Figure 3. Cutting tool diamond particle micro-morphology and cross-section profile
图 4 不同刀具角度下切削距离为16 nm时原子位移横截面
Figure 4. Cross-sectional snapshots of atomic displacement with a cutting distance of 16 nm at different tool rake angle and flank angle
图 5 不同刀具角度下切屑原子数随切削距离变化对比
Figure 5. Number of chip atoms against cutting distance under different tool angles
图 6 不同刀具角度切削的法向力与切向力随切削距离变化对比
Figure 6. Comparison of normal force and tangential force of different tool angle cutting with distance
图 7 位错和晶体结构截面示意图
Figure 7. Cross-sectional snapshots of dislocation and crystal structures
图 8 不同刀具角度下各晶体结构原子数对比图
Figure 8. Number of crystal structures atoms under different angles
图 9 不同刀具角度下亚表层损伤厚度
Figure 9. Thickness of sub-surface damage layer under different tool angles
图 11 不同刀具角度下位错线长度随切削距离变化对比图
Figure 11. Comparison of dislocation line length with cutting distance under different tool angles
图 12 前、后角为18°时刀具切削区原子的配位数分布示意图
Figure 12. A schematic diagram of CNs in cutting zone of tool with rake angle of 18°
图 13 不同刀具角度下各配位数原子数量对比图
Figure 13. Number of CNs against cutting distance under different tool angles
图 15 不同刀具角度下平均剪切应变和米塞斯应力随切削距离的变化对比
Figure 15. Comparison of average shear strain and von Mises stress with cutting distance under different tool angles
图 16 不同刀具角度下平均温度随切削距离变化对比图
Figure 16. Average temperature against cutting distance under different tool angles
图 17 实验获得的切削沟槽局部显微形貌及其截面TEM图像
Figure 17. Localized topographies and TEM images of grooves cut using diamond grits
表 1 单晶GaN纳米切削仿真参数
Table 1. Simulation parameters of nanocutting for single crystal GaN
项目 / 参数 类型 / 取值 工件 GaN 刀具 金刚石 工件尺寸 / nm 24 × 16 × 10 原子数 n / 个 324 786 前角 γ / (°) −18, −12, −6, 6, 12, 18 后角 α / (°) −18, −12, −6, 6, 12, 18 切削深度 d / nm 3 初始温度 T / K 293 切削方向 （0001）晶面[−2110]晶向 切削距离 s / nm 16 积分步长 t / fs 1 切削速度 v / (m·s−1) 50 
下载: 导出CSV
表 2 C-Ga和C-N间相互作用的L-J势函数参数
Table 2. Lennard-Jones potential for C-Ga and C-N interactions
作用对 平衡距离 ε / Å 内聚能 σ / meV C-Ga 3.691 9 8.464 6 C-N 3.367 7 3.723 5
下载: 导出CSV
-
[1] FUJIKANE M, YOKOGAWA T, NAGAO S, et al. Nanoindentation study on insight of plasticity related to dislocation density and crystal orientation in GaN [J]. Applied Physics Letters,2012,101(20):201901. doi: 10.1063/1.4767372 [2] PUST P, SCHMIDT P J, SCHNICK W. A revolution in lighting [J]. Nature Materials,2015,14(5):454-458. doi: 10.1038/nmat4270 [3] TSAO J Y, CRAWFORD M H, COLTRIN M E, et al. Toward smart and ultra-efficient solid-state lighting [J]. Advanced Optical Materials,2014,2(9):809-836. doi: 10.1002/adom.201400131 [4] MISHRA U K, SHEN L K, KAZIOR T E, et al. GaN-based RF power devices and amplifiers [J]. Proceedings of the IEEE,2008,96(2):287-305. doi: 10.1109/JPROC.2007.911060 [5] GAUDENZIO M, MATTEO M, ENRICO Z. Gallium nitride-enabled high frequency and high efficiency power conversion [M]. Springer International Publishing, 2018. [6] LAI M, ZHANG X D, FANG F Z, et al. Study on nanometric cutting of germanium by molecular dynamics simulation [J]. Nanoscale Research Letters,2013,8(1):13. doi: 10.1186/1556-276X-8-13 [7] WANG Q L, BAI Q S, CHEN J X, et al. Subsurface defects structural evolution in nano-cutting of single crystal copper [J]. Applied Surface Science,2015,344:38-46. doi: 10.1016/j.apsusc.2015.03.061 [8] WANG J S, ZHANG X D, FANG F Z, et al. Study on nano-cutting of brittle material by molecular dynamics using dynamic modeling [J]. Computational Materials Science,2020,183:109851. doi: 10.1016/j.commatsci.2020.109851 [9] WANG P C, YU J G, ZHANG Q X. Nano-cutting mechanical properties and microstructure evolution mechanism of amorphous/single crystal alloy interface [J]. Computational Materials Science,2020,184:109915. doi: 10.1016/j.commatsci.2020.109915 [10] ZHANG C Y, DONG Z G, YUAN S, et al. Study on subsurface damage mechanism of gallium nitride in nano-grinding [J]. Materials Science in Semiconductor Processing,2021,128:105760. doi: 10.1016/j.mssp.2021.105760 [11] ZHAO L, ZHANG J J, ZHANG J G, et al. Atomistic investigation of machinability of monocrystalline 3C–SiC in elliptical vibration-assisted diamond cutting [J]. Ceramics International,2021,47(2):2358-2366. doi: 10.1016/j.ceramint.2020.09.078 [12] YANG Z C, ZHU L D, ZHANG G X, et al. Review of ultrasonic vibration-assisted machining in advanced materials [J]. International Journal of Machine Tools and Manufacture,2020,156:103594. doi: 10.1016/j.ijmachtools.2020.103594 [13] LI C, PIAO Y C, MENG B B, et al. Phase transition and plastic deformation mechanisms induced by self-rotating grinding of GaN single crystals [J]. International Journal of Machine Tools and Manufacture,2022,172:103827. doi: 10.1016/j.ijmachtools.2021.103827 [14] SHUAI Z, HOUFU D. Effect of diamond grain shape on gallium nitride nano-grinding process [J]. Materials Science in Semiconductor Processing,2024,171:108034. doi: 10.1016/j.mssp.2023.108034 [15] LIU Q, LIAO Z R, AXINTE D. Temperature effect on the material removal mechanism of soft-brittle crystals at nano/micron scale [J]. International Journal of Machine Tools and Manufacture,2020,159:103620. doi: 10.1016/j.ijmachtools.2020.103620 [16] WANG B, KANG G Z, YU C, et al. Molecular dynamics simulations on one-way shape memory effect of nanocrystalline NiTi shape memory alloy and its cyclic degeneration [J]. International Journal of Mechanical Sciences,2021,211:106777. doi: 10.1016/j.ijmecsci.2021.106777 [17] HUANG H, LI X L, MU D K, et al. Science and art of ductile grinding of brittle solids [J]. International Journal of Machine Tools and Manufacture,2021,161:103675. doi: 10.1016/j.ijmachtools.2020.103675 [18] ZHAO H W, SHI C L, ZHANG P, et al. Research on the effects of machining-induced subsurface damages on mono-crystalline silicon via molecular dynamics simulation [J]. Applied Surface Science,2012,259:66-71. doi: 10.1016/j.apsusc.2012.06.087 [19] DAI H F, LI S B, CHEN G Y. Molecular dynamics simulation of subsurface damage mechanism during nanoscratching of single crystal silicon [J]. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology,2019,233(1):61-73. doi: 10.1177/1350650118765351 [20] KALKHORAN S N A, VAHDATI M, YAN J W. Effect of relative tool sharpness on subsurface damage and material recovery in nanometric cutting of mono-crystalline silicon: A molecular dynamics approach [J]. Materials Science in Semiconductor Processing,2020,108:104868. doi: 10.1016/j.mssp.2019.104868 [21] KALKHORAN S N A, VAHDATI M, YAN J W. Molecular dynamics investigation of nanometric cutting of single-crystal silicon using a blunt tool [J]. JOM,2019,71(12):4296-4304. doi: 10.1007/s11837-019-03671-w [22] ZHAO P Y, GAO X F, ZHAO B, et al. Investigation on nano-grinding process of GaN using molecular dynamics simulation: Nano-grinding parameters effect [J]. Journal of Manufacturing Processes,2023,102:429-442. doi: 10.1016/j.jmapro.2023.07.046 [23] XU F F, FANG F Z, ZHANG X D. Side flow effect on surface generation in nano cutting [J]. Nanoscale Research Letters,2017,12(1):359. doi: 10.1186/s11671-017-2136-3 [24] ABDULKADIR L N, BELLO A A, BAWA M A, et al. Nanometric behaviour of monocrystalline silicon when single point diamond turned: A molecular dynamics and response surface methodology analysis [J]. Engineering Research Express,2020,2(3):035038. doi: 10.1088/2631-8695/abb6dd [25] WANG Y Q, TANG S, GUO J. Molecular dynamics study on deformation behaviour of monocrystalline GaN during nano abrasive machining [J]. Applied Surface Science,2020,510:145492. doi: 10.1016/j.apsusc.2020.145492 [26] WANG Y Q, GUO J. Effect of abrasive size on nano abrasive machining for wurtzite GaN single crystal via molecular dynamics study [J]. Materials Science in Semiconductor Processing,2021,121:105439. doi: 10.1016/j.mssp.2020.105439 [27] LIU L, EDGAR J. Substrates for gallium nitride epitaxy [J]. Materials Science & Engineering R,2002,37(3):61-127. [28] PLIMPTON S. Fast parallel algorithms for short-range molecular dynamics [J]. Journal of Computational Physics,1995,117(1):1-19. doi: 10.1006/jcph.1995.1039 [29] STUKOWSKI A. Visualization and analysis of atomistic simulation data with OVITO: The open visualization tool [J]. Modelling Simulation in Material Science Engineering,2010,18(1):015012. doi: 10.1088/0965-0393/18/1/015012 [30] QIAN Y, DENG S Z, SHANG F L, et al. Dependence of tribological behavior of GaN crystal on loading direction: A molecular dynamics study [J]. Journal of Applied Physics,2019,126(7):075108. doi: 10.1063/1.5093227 [31] VERLET L. Computer "experiments" on classical fluids. I. thermody-namical properties of lennard-Jones molecules [J]. Physical Review,1967,159(1):98-103. doi: 10.1103/PhysRev.159.98 [32] XIANG H G, LI H T, FU T, et al. Formation of prismatic loops in AlN and GaN under nanoindentation [J]. Acta Materialia,2017,138:131-139. doi: 10.1016/j.actamat.2017.06.045 [33] BÉRÉ A, SERRA A. On the atomic structures, mobility and interactions of extended defects in GaN: Dislocations, tilt and twin boundaries [J]. Philosophical Magazine,2006,86(15):2159-2192. doi: 10.1080/14786430600640486 [34] STILLINGER F H, WEBER T A. Computer simulation of local order in condensed phases of silicon [J]. Physical Review B,1985,31(8):5262-5271. doi: 10.1103/PhysRevB.31.5262 [35] TERSOFF J. Modeling solid-state chemistry: Interatomic potentials for multicomponent systems [J]. Physical Review B,1989,39(8):5566. doi: 10.1103/PhysRevB.39.5566 [36] MAYO S L, OLAFSON B D, GODDARD W A. DREIDING: A generic force field for molecular simulations [J]. The Journal of Physical Chemistry,1990,94(26):8897-8909. doi: 10.1021/j100389a010 [37] ISONO Y, TANAKA T. Three-dimensional molecular dynamics simulation of atomic scale precision processing using a pin tool [J]. JSME International Journal Series A,1997,40(3):211-218. doi: 10.1299/jsmea.40.211 [38] GOEL S, LUO X C, REUBEN R L. Shear instability of nanocrystalline silicon carbide during nanometric cutting [J]. Applied Physics Letters,2012,100(23):231902. doi: 10.1063/1.4726036 [39] CROSS G L W. Isolation leads to change [J]. Nature Nanotechnology,2011,6(8):467-468. doi: 10.1038/nnano.2011.124 [40] SHIMIZU F, OGATA S, LI J. Theory of shear banding in metallic glasses and molecular dynamics calculations [J]. Materials Transactions,2007,48(11):2923-2927. doi: 10.2320/matertrans.MJ200769 [41] SARASAMAK K, KULKARNI A J, ZHOU M, et al. Stability of wurtzite, unbuckled wurtzite, and rocksalt phases of SiC, GaN, InN, ZnO, and CdSe under loading of different triaxialities [J]. Physical Review B,2008,77(2):024104. doi: 10.1103/PhysRevB.77.024104 [42] QIAN Y, SHANG F L, WAN Q, et al. A molecular dynamics study on indentation response of single crystalline wurtzite GaN [J]. Journal of Applied Physics,2018,124(11):115102. doi: 10.1063/1.5041738 [43] STUKOWSKI A, BULATOV V V, ARSENLIS A. Automated identification and indexing of dislocations in crystal interfaces [J]. Modelling and Simulation in Materials Science and Engineering,2012,20(8):085007. doi: 10.1088/0965-0393/20/8/085007 [44] STUKOWSKI A, ALBE K. Extracting dislocations and non-dislocation crystal defects from atomistic simulation data [J]. Modelling and Simulation in Materials Science and Engineering,2010,18(8):085001. doi: 10.1088/0965-0393/18/8/085001 [45] WILLIAMS B E, GLASS J T. Characterization of diamond thin films: Diamond phase identification, surface morphology, and defect structures [J]. Journal of Materials Research,1989,4(2):373-384. doi: 10.1557/JMR.1989.0373 [46] WANG H, DONG Z G, YUAN S, et al. Effects of tool geometry on tungsten removal behavior during nano-cutting [J]. International Journal of Mechanical Sciences,2022,225:107384. doi: 10.1016/j.ijmecsci.2022.107384 [47] WU Y, RAO Q, QIN Z, et al. A distinctive material removal mechanism in the diamond grinding of (0001)-oriented single crystal gallium nitride and its implications in substrate manufacturing of brittle materials [J]. International Journal of Machine Tools and Manufacture,2024,203:104222. doi: 10.1016/j.ijmachtools.2024.104222 [48] LI C, PIAO Y C, MENG B B, et al. Anisotropy dependence of material removal and deformation mechanisms during nanoscratch of gallium nitride single crystals on (0001) plane [J]. Applied Surface Science,2022,578:152028. doi: 10.1016/j.apsusc.2021.152028 [49] AHN Y, FARRIS T N, CHANDRASEKAR S. Sliding micro indentation fracture of brittle materials: Role of elastic stress fields [J]. Mechanics of Materials,1998,29(3/4):143-152. [50] ZHANG L, ZHAO H W, MA Z C, et al. A study on phase transformation of monocrystalline silicon due to ultra-precision polishing by molecular dynamics simulation [J]. AIP Advances,2012,2(4):042116. doi: 10.1063/1.4763462 [51] GAO T H, MAO S Y, LI L X, et al. Effect of graphene on the surface nanomechanical behavior and subsurface layer of GaN damage during nanogrinding using molecular dynamics simulation [J]. Micro and Nanostructures,2023,184:207694. doi: 10.1016/j.micrna.2023.207694 [52] BEREND D, BENJAMIN B, TOBIAS P, et al. Modeling of stresses at the cutting wedge in the interrupted cut for the design of the cutting edge microgeometry [J]. Procedia CIRP,2023,117:299-304. doi: 10.1016/j.procir.2023.03.051 [53] TIAN C J, WENG J, ZHUANG K J, et al. The role of tool edge geometry on material removal and surface integrity in cutting metal matrix composites [J]. Journal of Manufacturing Processes,2025,137:135-149. doi: 10.1016/j.jmapro.2025.01.096 -
点击查看大图
图(17) / 表(2)
计量
- 文章访问数: 19
- HTML全文浏览量: 7
- PDF下载量: 0
- 被引次数: 0
邮件订阅
RSS
