- Email: [email protected]
Assessing microstructure changes in potassium dihydrogen phosphate crystals induced by mechanical stresses
Scripta Materialia 113 (2016) 48–50
Contents lists available at ScienceDirect
Scripta Materialia journal homepage: www.elsevier.com/locate/smm
Regular Article
Assessing microstructure changes in potassium dihydrogen phosphate crystals induced by mechanical stresses Ning Hou a,b, Yong Zhang a,b,⁎, Liangchi Zhang c,⁎⁎, Feihu Zhang a a b c
School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001, China Ministry of Education Key Laboratory of Micro-systems and Micro-structures Manufacturing, Harbin Institute of Technology, Harbin 150001, China Laboratory for Precision and Nano Processing Technologies, University of New South Wales, NSW 2052, Australia
a r t i c l e
i n f o
Article history: Received 10 August 2015 Accepted 2 October 2015 Available online 22 October 2015 Keywords: Grazing incidence X-ray diffraction KDP crystals Microstructure changes Laser damage threshold
a b s t r a c t This paper proposes a new way of damage characterization with the aid of the grazing incidence X-ray diffraction technique. The results showed that a machined potassium dihydrogen phosphate (KDP) crystal contains a lattice misalignment structure in its shallow subsurface layer. Dislocation motions are the primary mechanism of the structural evolution from the KDP's monocrystalline to the misaligned crystalline structure. These findings allow to identify the underlying causes of lower laser damage threshold (LDT) of KDP components produced by ultra-precision machining. © 2015 Elsevier Ltd. All rights reserved.
Potassium dihydrogen phosphate (KDP) crystals have excellent optical properties such as high nonlinear conversion efficiency, superior photoelectric and piezoelectric properties, good optical homogeneity, easy phase matching and excellent transparency in a wide range of optical spectra [1–3]. Since the successful growth of large KDP crystals of 400 to 500 mm in diameter [4], they have become a key nonlinear material of the optical switching and frequency conversion components for the laser ignition facility of inertial confinement fusion (ICF) [5]. However, the laser-induced damages (LID) often emerge in the bulk and surface of the KDP components. This has significantly affected the output power of a high-energy laser system. Hence, many efforts have been to explore the possible mechanisms of LID from the aspects of KDP crystal growth [6,7] to laser working conditions [8,9]. To date, however, the damage mechanisms are still unclear. In particular, the influence of surface/subsurface damage of KDP crystals caused during KDP lens surfacing has not been systematically addressed. Such a damaged subsurface could have brought about unexpected laser focusing inside a KDP component, causing bulk damages in a KDP element [10]. Some recent nanoindentation studies revealed that the mechanical properties of KDP have been conspicuously altered by mechanical finishing processes, suggesting that the laser damage threshold (LDT) of KDP is very much affected by the subsurface damage during mechanical surfacing [11].
⁎ Correspondence to: Y. Zhang, School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001, China. ⁎⁎ Corresponding author. E-mail addresses: [email protected] (Y. Zhang), [email protected] (L. Zhang).
http://dx.doi.org/10.1016/j.scriptamat.2015.10.002 1359-6462/© 2015 Elsevier Ltd. All rights reserved.
Smooth KDP surfaces, with surface roughness Ra of a few nanometers, can be produced by various ultra-precision machining processes [12–14]. Some methods have been tried to detect the subsurface damage thus induced [15]. Although optical, mechanical and chemical means have been used to explore the subsurface damages of other optic materials [16,17], they are difficult to apply in the case of KDP because a KDP crystal is sensitive to temperature variation, deliquescence and contact stresses. In addition, these methods cannot be used to identify the microstructures of subsurface damages in a KDP crystal. As a result, the understanding of the types and mechanisms of subsurface damages in KDP is still unavailable. This paper presents a new method, using the grazing incidence Xray diffraction (GIXD), to more precisely evaluate the subsurface structure of a KDP crystal and to analyze the formation mechanisms of the subsurface damages. The KDP crystal specimens used in this study were produced with the rapid growth technique by the State Key Laboratory of Crystal Materials, Shandong University, China [18]. The KDP crystal has a tetragonal structure at room temperature [19]. The paraelectric phase is the I-42d space group; and the ferroelectric phase is the Fdd2 space group. Its paraelectric–ferroelectric transition temperature is 122 K [20]. The material's mechanical properties have been reported in the literatures [21,22]. The specimen size was 50 mm × 10 mm × 13 mm. The ultra-precision surface machining experiments were conducted on a fly-cutting machine, during which a KDP crystal specimen was clamped by the vacuum chuck on the feed table. The cutting speed of the diamond cutting tip on the fly-cutting head was 13.2 m/s, with the feed rate f being 60 μm/s, cutting depth ap being 5 μm, and tool rake angle γ0 being −45°.
N. Hou et al. / Scripta Materialia 113 (2016) 48–50
49
Fig. 1. A schematic diagram of the GIXD in which α is the angle of incidence, β the angle of emergence, and 2θ the angle of diffraction.
The GIXD experiments were performed to explore the subsurface structures of the KDP crystals after fly-cutting, on an Empyrean X-ray diffractometer (PANalytical, Netherlands) with ceramic X-ray tubes and Cu radiation. Fig. 1 shows the schematic diagram of the GIXD method [23,24]. It is a non-destructive and non-contact method to guarantee that the original state of the specimens could be maintained. Another advantage of the method is that unlike the conventional X-ray diffraction method, the GIXD can effectively avoid the signals from the bulk when detecting the subsurface structure of a material. Fig. 2 shows the XRD pattern of the bulk KDP crystal. As can be seen, there is only a strong major diffraction peak corresponding to (112), suggesting that the material is a perfect single crystal. The small peak at the diffraction angle of 30.7° indicates that there might be certain residual stresses or impurity in the bulk crystal. The surface/subsurface or near surface structures of the machined KDP crystal were assessed by using the GIXD, as shown in Fig. 3. Curve (a) in Fig. 3 shows that there are six diffraction peaks, corresponding to six Miller indices. The intensities on (200), (112) and (312) planes are stronger. These diffraction peaks coincide well with the Powder Diffraction Standards of KDP crystal. It can be seen that the intensity of the (112) peak of the KDP crystal bulk in Fig. 2 is about 2747 times greater than that in Curve (a) of Fig. 3. The presence of different diffraction peaks implies that the subsurface structure of the KDP crystal after machining has become a lattice misaligned structure (LMS). It is interesting to note that the diffraction pattern at the grazing incidence angle of 2°, as shown in Curve (b) of Fig. 3, is obviously different from that in Curve (a). In the former, the peaks corresponding to (101), (220) and
Fig. 2. XRD analysis of KDP crystal bulk.
Fig. 3. GIXD analysis of a machined KDP crystal surface. (a) Grazing incidence angle α = 1°, and (b) grazing incidence angle α = 2°.
(301) planes are absent; an additional diffraction peak of (303) plane emerges; and the intensities of peaks (200), (112) and (312) are much smaller than those in Curve (a) at α = 1°. These imply that the LMS is still persisted at the depth of subsurface of which the X-ray beam can penetrate with α = 2°, but that the LMS content becomes less. According to the principle of GIXD, the bigger the incident angle α is, the deeper the X-ray penetrates. This indicates that the LMS layer induced by surface machining is very shallow. The above analysis shows that the bulk material of the KDP remains as a single crystal after surface machining, a shallow subsurface layer has turned to a LMS as shown by the (112), (312), (200), (101), (220), (301) and (303) plane peaks in Fig. 3. The existence of these planes has a close relationship with the slip systems of a KDP crystal. According to literature [25], there are two slip systems during KDP deformation. One is in the planes (110), (101), (112), and (123) with a common Burgers vector 1/2[111] and the other is the (010)[100] system. It can be seen from Fig. 4 that the appearance of (101) and (112) planes is fully identical with the slip system, while (312) plane is close to (112) and (123)1/2[111] slip systems, (301) and (303) planes are closer to the (101)1/2[111] slip system. The shear stresses induced by machining make the material deform more easily along these slip systems. Nevertheless, the hydrostatic stress caused by the cutting tip plays a more important role in the formation of the (200) and (220) planes. These suggest that dislocations imitate from the tool-KDP
Fig. 4. The positions of diffraction peak planes in the KDP unit cell.
50
N. Hou et al. / Scripta Materialia 113 (2016) 48–50
contact zone during the machining and then extend to forming slip bands in the KDP substrate [25]. Indeed, it has been discovered that mechanical machining can significantly affect the mechanical properties and optical performance of KDP crystals [11]. Our analysis and findings highlighted above demonstrate that such property alteration by machining would be attributed to the variation of the micro-structures in the KDP subsurface, because LMS has been produced. The energy at the misalignment boundaries is higher than that in the interior of a damage-free KDP crystal [26]. As a result, the misaligned KDP structures are easy to lead to LID in the surface/subsurface because the LID formation is due to ultrafast local material melting, resulting in plastic deformation and fracture of the surrounding material [27]. Moreover, the LMS and residual stresses have a great effect on the homogeneity of refractive index [28], which could perform as a set of micro/nano-lenses to divert a laser beam to focus in the interior of the KDP [29]. Such self-focusing significantly affects the laser intensity threshold for bulk damage. This study has for the first time discovered that the ultra-precision surface machining can create a lattice misalignment structure layer in the subsurface of a KDP single crystal. The misalignments are along (112), (312), (200), (101), (301), (303) and (220) planes while machining on a (112) bulk KDP crystal. These planes coincide with the slip systems of the KDP crystal, indicating that dislocation motions play an important role on the evolution of the subsurface structure. Such subsurface damages influence the LID of KDP crystals. This work was financially sponsored by NSFC (Grant No. 51375122). References [1] W.P. Mason, Phys. Rev. 69 (1946) 173. [2] R. Stephen Craxton, Stephen D. Jacobs, Joseph E. Rizzo, Robert Boni, IEEE J. Quantum Electron. 17 (1981) 1782. [3] D. Eimerl, Ferroelectrics 72 (1987) 95.
[4] N.P. Zaitseva, J.J. De Yoreo, M.R. Dehaven, R.L. Vital, K.E. Montgomery, M. Richardson, L.J. Atherton, J. Cryst. Growth 180 (1997) 255. [5] J.J. De Yoreo, A.K. Burnham, P.K. Whitman, Int. Mater. Rev. 47 (2002) 113. [6] Y. Nishida, A. Yokotani, T. Sasaki, K. Yoshida, T. Yamanaka, C. Yamanaka, Appl. Phys. Lett. 52 (1988) 420. [7] A. Yokotani, T. Sasaki, K. Yoshida, T. Yamanaka, C. Yamanaka, Appl. Phys. Lett. 48 (1986) 1030. [8] P. DeMange, C.W. Carr, H.B. Radousky, S.G. Demos, SPIE 5337 (2004) 47. [9] C.W. Carr, M.D. Feit, A.M. Rubenchik, J.B. Trenholme, M.L. Spaeth, SPIE 5991 (2005) (59911Q-1). [10] E.L. Dawes, J.H. Marburger, Phys. Rev. 179 (1969) 862. [11] Y. Zhang, L.C. Zhang, M. Liu, F.H. Zhang, K. Mylvaganam, W.D. Liu, Revealing the mechanical properties of KDP crystals by nanoindentation, Mater. Sci. Eng. A (2015) (submitted for publication). [12] Baruch A. Fuchs, P. Paul Hed, Phillip C. Baker, Appl. Opt. 25 (1986) 1733. [13] Yoshiharu Namba, Masanori Katagiri, Masahiro Nakatsuka, J. Jpn. Soc. Precis. Eng. 64 (1998) 1487. [14] Richard C. Montesanti, Samuel L. Thompson, Coal and Electricity Div, U.S. USDOE Economic Regulatory Administration, Washington, DC, 1995 1–9. [15] Guipeng Tie, Yifan Dai, Chaoliang Guan, Shaoshan Chen, Bing Song, Opt. Eng. 52 (2013) (033401–1). [16] Jian Wang, Yaguo Li, Jinghua Han, Qiao Xu, Yinbiao Guo, J. Eur. Opt. Soc. Rapid 6 (2011) (11001–1). [17] Jian Shen, Shouhua Liu, Kui Yi, Hongbo He, Jianda Shao, Zhengxiu Fan, Opt. Int. J. Light Electron Opt. 116 (2005) 288. [18] Y.J. Fu, Z.S. Gao, X. Sun, S.L. Wang, Y.P. Li, H. Zeng, J.P. Luo, A.D. Duan, J.Y. Wang, Prog. Cryst. Growth Charact. Mater. 40 (2000) 211. [19] Qing Zhang, F. Chen, Nicholas Kioussis, S.G. Demos, H.B. Radousky, Phys. Rev. B 65 (2001) (024108–1). [20] Yuki Kobayashi, Shoichi Endo, Kichiro Koto, Takumi Kikegawa, Osamu Shimomura, Phys. Rev. B 51 (1995) 9302. [21] Jing Peng, Liangchi Zhang, Xinchun Lu, Mater. Sci. Forum 773–774 (2014) 713. [22] Yong Zhang, Liangchi Zhang, Mei Liu, Feihu Zhang, Kausala Mylvaganam, Weidong Liu, Wear 332–333 (2015) 900. [23] D. Gloaguen, J. Fajoui, B. Girault, Acta Mater. 71 (2014) 136. [24] Paul Angerer, Stefan Strobl, Acta Mater. 77 (2014) 370. [25] Chan Hai Guin, M.D. Katrich, A.I. Savinkov, M.P. Shaskolskaya, Krist. Tech. 15 (1980) 479. [26] S. Weissmann, J. Appl. Phys. 27 (1956) 389. [27] S.O. Kucheyev, W.J. Siekhaus, T.A. Land, S.G. Demos, Appl. Phys. Lett. 84 (2004) 2274. [28] Sheng-jun Zhu, Sheng-lai Wang, Liu Lin, Duan-liang Wang, Li Wei-dong, Huang Ping-ping, Xin-guang Xu, Acta Phys. Sin. 63 (2014) (107701–1). [29] Chris B. Schaffer, Andre Brodeur, Eric Mazur, Meas. Sci. Technol. 12 (2001) 1784.
Contents lists available at ScienceDirect
Scripta Materialia journal homepage: www.elsevier.com/locate/smm
Regular Article
Assessing microstructure changes in potassium dihydrogen phosphate crystals induced by mechanical stresses Ning Hou a,b, Yong Zhang a,b,⁎, Liangchi Zhang c,⁎⁎, Feihu Zhang a a b c
School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001, China Ministry of Education Key Laboratory of Micro-systems and Micro-structures Manufacturing, Harbin Institute of Technology, Harbin 150001, China Laboratory for Precision and Nano Processing Technologies, University of New South Wales, NSW 2052, Australia
a r t i c l e
i n f o
Article history: Received 10 August 2015 Accepted 2 October 2015 Available online 22 October 2015 Keywords: Grazing incidence X-ray diffraction KDP crystals Microstructure changes Laser damage threshold
a b s t r a c t This paper proposes a new way of damage characterization with the aid of the grazing incidence X-ray diffraction technique. The results showed that a machined potassium dihydrogen phosphate (KDP) crystal contains a lattice misalignment structure in its shallow subsurface layer. Dislocation motions are the primary mechanism of the structural evolution from the KDP's monocrystalline to the misaligned crystalline structure. These findings allow to identify the underlying causes of lower laser damage threshold (LDT) of KDP components produced by ultra-precision machining. © 2015 Elsevier Ltd. All rights reserved.
Potassium dihydrogen phosphate (KDP) crystals have excellent optical properties such as high nonlinear conversion efficiency, superior photoelectric and piezoelectric properties, good optical homogeneity, easy phase matching and excellent transparency in a wide range of optical spectra [1–3]. Since the successful growth of large KDP crystals of 400 to 500 mm in diameter [4], they have become a key nonlinear material of the optical switching and frequency conversion components for the laser ignition facility of inertial confinement fusion (ICF) [5]. However, the laser-induced damages (LID) often emerge in the bulk and surface of the KDP components. This has significantly affected the output power of a high-energy laser system. Hence, many efforts have been to explore the possible mechanisms of LID from the aspects of KDP crystal growth [6,7] to laser working conditions [8,9]. To date, however, the damage mechanisms are still unclear. In particular, the influence of surface/subsurface damage of KDP crystals caused during KDP lens surfacing has not been systematically addressed. Such a damaged subsurface could have brought about unexpected laser focusing inside a KDP component, causing bulk damages in a KDP element [10]. Some recent nanoindentation studies revealed that the mechanical properties of KDP have been conspicuously altered by mechanical finishing processes, suggesting that the laser damage threshold (LDT) of KDP is very much affected by the subsurface damage during mechanical surfacing [11].
⁎ Correspondence to: Y. Zhang, School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001, China. ⁎⁎ Corresponding author. E-mail addresses: [email protected] (Y. Zhang), [email protected] (L. Zhang).
http://dx.doi.org/10.1016/j.scriptamat.2015.10.002 1359-6462/© 2015 Elsevier Ltd. All rights reserved.
Smooth KDP surfaces, with surface roughness Ra of a few nanometers, can be produced by various ultra-precision machining processes [12–14]. Some methods have been tried to detect the subsurface damage thus induced [15]. Although optical, mechanical and chemical means have been used to explore the subsurface damages of other optic materials [16,17], they are difficult to apply in the case of KDP because a KDP crystal is sensitive to temperature variation, deliquescence and contact stresses. In addition, these methods cannot be used to identify the microstructures of subsurface damages in a KDP crystal. As a result, the understanding of the types and mechanisms of subsurface damages in KDP is still unavailable. This paper presents a new method, using the grazing incidence Xray diffraction (GIXD), to more precisely evaluate the subsurface structure of a KDP crystal and to analyze the formation mechanisms of the subsurface damages. The KDP crystal specimens used in this study were produced with the rapid growth technique by the State Key Laboratory of Crystal Materials, Shandong University, China [18]. The KDP crystal has a tetragonal structure at room temperature [19]. The paraelectric phase is the I-42d space group; and the ferroelectric phase is the Fdd2 space group. Its paraelectric–ferroelectric transition temperature is 122 K [20]. The material's mechanical properties have been reported in the literatures [21,22]. The specimen size was 50 mm × 10 mm × 13 mm. The ultra-precision surface machining experiments were conducted on a fly-cutting machine, during which a KDP crystal specimen was clamped by the vacuum chuck on the feed table. The cutting speed of the diamond cutting tip on the fly-cutting head was 13.2 m/s, with the feed rate f being 60 μm/s, cutting depth ap being 5 μm, and tool rake angle γ0 being −45°.
N. Hou et al. / Scripta Materialia 113 (2016) 48–50
49
Fig. 1. A schematic diagram of the GIXD in which α is the angle of incidence, β the angle of emergence, and 2θ the angle of diffraction.
The GIXD experiments were performed to explore the subsurface structures of the KDP crystals after fly-cutting, on an Empyrean X-ray diffractometer (PANalytical, Netherlands) with ceramic X-ray tubes and Cu radiation. Fig. 1 shows the schematic diagram of the GIXD method [23,24]. It is a non-destructive and non-contact method to guarantee that the original state of the specimens could be maintained. Another advantage of the method is that unlike the conventional X-ray diffraction method, the GIXD can effectively avoid the signals from the bulk when detecting the subsurface structure of a material. Fig. 2 shows the XRD pattern of the bulk KDP crystal. As can be seen, there is only a strong major diffraction peak corresponding to (112), suggesting that the material is a perfect single crystal. The small peak at the diffraction angle of 30.7° indicates that there might be certain residual stresses or impurity in the bulk crystal. The surface/subsurface or near surface structures of the machined KDP crystal were assessed by using the GIXD, as shown in Fig. 3. Curve (a) in Fig. 3 shows that there are six diffraction peaks, corresponding to six Miller indices. The intensities on (200), (112) and (312) planes are stronger. These diffraction peaks coincide well with the Powder Diffraction Standards of KDP crystal. It can be seen that the intensity of the (112) peak of the KDP crystal bulk in Fig. 2 is about 2747 times greater than that in Curve (a) of Fig. 3. The presence of different diffraction peaks implies that the subsurface structure of the KDP crystal after machining has become a lattice misaligned structure (LMS). It is interesting to note that the diffraction pattern at the grazing incidence angle of 2°, as shown in Curve (b) of Fig. 3, is obviously different from that in Curve (a). In the former, the peaks corresponding to (101), (220) and
Fig. 2. XRD analysis of KDP crystal bulk.
Fig. 3. GIXD analysis of a machined KDP crystal surface. (a) Grazing incidence angle α = 1°, and (b) grazing incidence angle α = 2°.
(301) planes are absent; an additional diffraction peak of (303) plane emerges; and the intensities of peaks (200), (112) and (312) are much smaller than those in Curve (a) at α = 1°. These imply that the LMS is still persisted at the depth of subsurface of which the X-ray beam can penetrate with α = 2°, but that the LMS content becomes less. According to the principle of GIXD, the bigger the incident angle α is, the deeper the X-ray penetrates. This indicates that the LMS layer induced by surface machining is very shallow. The above analysis shows that the bulk material of the KDP remains as a single crystal after surface machining, a shallow subsurface layer has turned to a LMS as shown by the (112), (312), (200), (101), (220), (301) and (303) plane peaks in Fig. 3. The existence of these planes has a close relationship with the slip systems of a KDP crystal. According to literature [25], there are two slip systems during KDP deformation. One is in the planes (110), (101), (112), and (123) with a common Burgers vector 1/2[111] and the other is the (010)[100] system. It can be seen from Fig. 4 that the appearance of (101) and (112) planes is fully identical with the slip system, while (312) plane is close to (112) and (123)1/2[111] slip systems, (301) and (303) planes are closer to the (101)1/2[111] slip system. The shear stresses induced by machining make the material deform more easily along these slip systems. Nevertheless, the hydrostatic stress caused by the cutting tip plays a more important role in the formation of the (200) and (220) planes. These suggest that dislocations imitate from the tool-KDP
Fig. 4. The positions of diffraction peak planes in the KDP unit cell.
50
N. Hou et al. / Scripta Materialia 113 (2016) 48–50
contact zone during the machining and then extend to forming slip bands in the KDP substrate [25]. Indeed, it has been discovered that mechanical machining can significantly affect the mechanical properties and optical performance of KDP crystals [11]. Our analysis and findings highlighted above demonstrate that such property alteration by machining would be attributed to the variation of the micro-structures in the KDP subsurface, because LMS has been produced. The energy at the misalignment boundaries is higher than that in the interior of a damage-free KDP crystal [26]. As a result, the misaligned KDP structures are easy to lead to LID in the surface/subsurface because the LID formation is due to ultrafast local material melting, resulting in plastic deformation and fracture of the surrounding material [27]. Moreover, the LMS and residual stresses have a great effect on the homogeneity of refractive index [28], which could perform as a set of micro/nano-lenses to divert a laser beam to focus in the interior of the KDP [29]. Such self-focusing significantly affects the laser intensity threshold for bulk damage. This study has for the first time discovered that the ultra-precision surface machining can create a lattice misalignment structure layer in the subsurface of a KDP single crystal. The misalignments are along (112), (312), (200), (101), (301), (303) and (220) planes while machining on a (112) bulk KDP crystal. These planes coincide with the slip systems of the KDP crystal, indicating that dislocation motions play an important role on the evolution of the subsurface structure. Such subsurface damages influence the LID of KDP crystals. This work was financially sponsored by NSFC (Grant No. 51375122). References [1] W.P. Mason, Phys. Rev. 69 (1946) 173. [2] R. Stephen Craxton, Stephen D. Jacobs, Joseph E. Rizzo, Robert Boni, IEEE J. Quantum Electron. 17 (1981) 1782. [3] D. Eimerl, Ferroelectrics 72 (1987) 95.
[4] N.P. Zaitseva, J.J. De Yoreo, M.R. Dehaven, R.L. Vital, K.E. Montgomery, M. Richardson, L.J. Atherton, J. Cryst. Growth 180 (1997) 255. [5] J.J. De Yoreo, A.K. Burnham, P.K. Whitman, Int. Mater. Rev. 47 (2002) 113. [6] Y. Nishida, A. Yokotani, T. Sasaki, K. Yoshida, T. Yamanaka, C. Yamanaka, Appl. Phys. Lett. 52 (1988) 420. [7] A. Yokotani, T. Sasaki, K. Yoshida, T. Yamanaka, C. Yamanaka, Appl. Phys. Lett. 48 (1986) 1030. [8] P. DeMange, C.W. Carr, H.B. Radousky, S.G. Demos, SPIE 5337 (2004) 47. [9] C.W. Carr, M.D. Feit, A.M. Rubenchik, J.B. Trenholme, M.L. Spaeth, SPIE 5991 (2005) (59911Q-1). [10] E.L. Dawes, J.H. Marburger, Phys. Rev. 179 (1969) 862. [11] Y. Zhang, L.C. Zhang, M. Liu, F.H. Zhang, K. Mylvaganam, W.D. Liu, Revealing the mechanical properties of KDP crystals by nanoindentation, Mater. Sci. Eng. A (2015) (submitted for publication). [12] Baruch A. Fuchs, P. Paul Hed, Phillip C. Baker, Appl. Opt. 25 (1986) 1733. [13] Yoshiharu Namba, Masanori Katagiri, Masahiro Nakatsuka, J. Jpn. Soc. Precis. Eng. 64 (1998) 1487. [14] Richard C. Montesanti, Samuel L. Thompson, Coal and Electricity Div, U.S. USDOE Economic Regulatory Administration, Washington, DC, 1995 1–9. [15] Guipeng Tie, Yifan Dai, Chaoliang Guan, Shaoshan Chen, Bing Song, Opt. Eng. 52 (2013) (033401–1). [16] Jian Wang, Yaguo Li, Jinghua Han, Qiao Xu, Yinbiao Guo, J. Eur. Opt. Soc. Rapid 6 (2011) (11001–1). [17] Jian Shen, Shouhua Liu, Kui Yi, Hongbo He, Jianda Shao, Zhengxiu Fan, Opt. Int. J. Light Electron Opt. 116 (2005) 288. [18] Y.J. Fu, Z.S. Gao, X. Sun, S.L. Wang, Y.P. Li, H. Zeng, J.P. Luo, A.D. Duan, J.Y. Wang, Prog. Cryst. Growth Charact. Mater. 40 (2000) 211. [19] Qing Zhang, F. Chen, Nicholas Kioussis, S.G. Demos, H.B. Radousky, Phys. Rev. B 65 (2001) (024108–1). [20] Yuki Kobayashi, Shoichi Endo, Kichiro Koto, Takumi Kikegawa, Osamu Shimomura, Phys. Rev. B 51 (1995) 9302. [21] Jing Peng, Liangchi Zhang, Xinchun Lu, Mater. Sci. Forum 773–774 (2014) 713. [22] Yong Zhang, Liangchi Zhang, Mei Liu, Feihu Zhang, Kausala Mylvaganam, Weidong Liu, Wear 332–333 (2015) 900. [23] D. Gloaguen, J. Fajoui, B. Girault, Acta Mater. 71 (2014) 136. [24] Paul Angerer, Stefan Strobl, Acta Mater. 77 (2014) 370. [25] Chan Hai Guin, M.D. Katrich, A.I. Savinkov, M.P. Shaskolskaya, Krist. Tech. 15 (1980) 479. [26] S. Weissmann, J. Appl. Phys. 27 (1956) 389. [27] S.O. Kucheyev, W.J. Siekhaus, T.A. Land, S.G. Demos, Appl. Phys. Lett. 84 (2004) 2274. [28] Sheng-jun Zhu, Sheng-lai Wang, Liu Lin, Duan-liang Wang, Li Wei-dong, Huang Ping-ping, Xin-guang Xu, Acta Phys. Sin. 63 (2014) (107701–1). [29] Chris B. Schaffer, Andre Brodeur, Eric Mazur, Meas. Sci. Technol. 12 (2001) 1784.