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SiC heterojunction prepared by metal induced crystallization of amorphous silicon
Materials Letters 188 (2017) 409–412
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Si/SiC heterojunction prepared by metal induced crystallization of amorphous silicon Yuan Zang a, Lian-bi Li b,n, Jing An a, Lei Huang a, Hai Li Jin c a
Department of Electronic Engineering, Xi’an University of Technology, Xi’an 710048, China School of Science, Xi’an Polytechnic University, Xi’an 710048, China c Colloge of stomatology, Xi’an Jiaotong University, Xi’an 710004, China b
art ic l e i nf o
a b s t r a c t
Article history: Received 21 September 2016 Received in revised form 19 November 2016 Accepted 22 November 2016 Available online 29 November 2016
In this work, amorphous Si films were prepared on 6H-SiC(0001) by PECVD and induced to be crystalline structure at 400 °C 700 °C by Ni to form c-Si/6H-SiC heterojunction. Raman and XRD results indicated that ɑ-Si films on 6H-SiC transforms to c-Si after 600 °C induced annealing, and the Si films with o 111 4 and o110 4 preferred orientations have larger grain size and higher crystalline quality. TEM results indicated the c-Si films are polycrystalline structure with a lattice constant of 5.43 Å, which are consistent with c-Si. It was demonstrated that Ni promotes the crystallization of the ɑ-Si films on 6H-SiC at low temperature significantly. & 2016 Elsevier B.V. All rights reserved.
Keywords: Si/SiC heterostructure Metal induced crystallization Raman spectra TEM
1. Introduction
2. Experiments
Silicon carbide (SiC) is an excellent material candidate for power devices due to its outstanding physical properties [1]. However, with the wide bandgap, SiC-based photoelectric devices can be only driven by ultraviolet (UV) light [2]. In order to expand SiC applications, Si/SiC heterojunction is suggested to make SiCbased devices to be light-activated by non-UV lights [3]. In our previous work, the Si/SiC heterojunctions with high growth temperatures were prepared on 6H-SiC (0001) C-face [4]. Nevertheless, structural defects caused by the lattice mismatch between Si/SiC heterojunction have a serious impact on the performance of the Si/SiC photodiode [5,6]. It is reported metal induced crystallization (MIC) of amorphous Si (ɑ-Si) can decrease the growth temperature and improve the crystallization of Si film [5,6]. Schmidt [7] and jin [8] reported a Silicon Thin Films Prepared by MIC method. Peng [9] reported a Au-induced amorphous Si1 xGex films at 400 °C. However, the MIC of the Si/SiC heterostructure is rarely reported. In this work, the ɑ-Si films has been prepared on 6H-SiC(0001) and induced to be crystallized structure by Ni to form c-Si/6H-SiC heterojunction. The crystallization characteristics of samples are investigated in details. It is revealed that Ni significantly promotes the crystallization of the ɑ-Si films on 6H-SiC at low temperature.
An n-type doped (doping concentration of 1017 cm 3) 6H-SiC wafer with a thickness of 300 mm was purchased from II-VI Inc.. Prior to the preparation of PECVD process, the 6H-SiC substrates were cleaned using the standard RCA method. The ɑ-Si films were prepared at 50 °C 300 °C with a growth pressure of 80 Pa for 45 min. Gas source used in this work was Silane (10%, dilute by H2). After the ɑ-Si growth, Ni films were sputtered on ɑ-Si films by RF magnetron sputtering at room temperature with RF power of 100 W for 15 min. And the ɑ-Si films were induced crystallization by Ni metal films at 400 °C 700 °C for 3 h. Infrared absorption spectrum (Shimadzu, FTIR-8400), X-ray diffraction (Shimadzu, XRD-7000), Raman spectrum (Renishaw inVia), transmission electron microscopy (TEM, JEM-3010) were employed to characterize the Si/SiC heterostructures.
n
Corresponding author. E-mail address: [email protected] (L.-b. Li).
http://dx.doi.org/10.1016/j.matlet.2016.11.079 0167-577X/& 2016 Elsevier B.V. All rights reserved.
3. Result and discussion Infrared absorption spectrum is introduced to discuss the different configuration of Si-H bond in ɑ-Si. Fig. 1 shows infrared absorption spectrum with growth temperatures of 65 °C 300 °C. There is only one absorption peak locates at 2090 cm 1, which belongs to the stretching vibration of H-Si-H bond [10]. As temperature increases from 65 °C to 300 °C, the absorption peak decreases accordingly. This demonstrates the content of hydrogen in ɑ-Si decreases.
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Y. Zang et al. / Materials Letters 188 (2017) 409–412
Fig. 1. Infrared absorption spectrum ofɑ-Si films prepared under different substrate temperature.
Raman spectra of Si films before and after Ni induced crystallization under different temperaturesare shown in Fig. 2. The broad and weak peaks observed near 480 cm 1 can be assigned to the ɑ-Si TO mode[11]. After 500 °C annealing, the Raman peak of the Si films shift to 500 cm 1. The peak was decomposed two peaks located at 480 cm 1 and 500 cm 1, which correspond to ɑ-
Si and intermediate Si. As annealing temperature increases to 600 °C and 700 °C, the Raman peak belong to c-Si at 520 cm 1 appears. This demonstrates that the ɑ-Si transforms to c-Si as the annealing temperature increases continuously. In Fig. 2(d), the Raman peak at 515 cm 1 can be decomposed to two peaks at 480 cm 1 and 515 cm 1, which corresponded to ɑ-Si and c-Si TO mode. The full width at half maximum (FWHM) values of the Raman peak at 515 cm 1 is 6.87. In Fig. 2(e), the FWHM values of the Raman peak at 517 cm 1 is 9.22, which is higher than the FWHM values annealed at 600 °C. This results indicate Si films with 600 °C annealing have larger grain size and higher crystalline quality. The Raman peak of c-Si (517 cm 1) was lower than the actual Si-Si bulk TO mode (520 cm 1) [12], which indicates ɑ-Si is not entirely induced to c-Si. The intensity of the Raman peak increases with increasing annealing temperatures due to improvements in the structural order [13]. The XRD patterns of the Si films after Ni induced crystallization under different annealing temperature were shown in Fig. 3. As temperature increases to 500 °C, the XRD peak at 2θ ¼28.5° [Si (111)] appears. Fig. 3(d) and Fig. 3(e) show XRD patterns with annealing temperature of 600 °C and 700 °C. There are three XRD peaks at 2θ ¼ 28.5°, 47.3° and 56.1°, which are corresponding to Si (111), Si (220) and Si (311), respectively. It is shown that ɑ-Si is induced to polycrystalline structure by Ni catalysis. Because of the lowest free energy than other directions, (111)peak is dominating in Fig. 3(d) and Fig. 3(e)[14]. The FWHM values of Si(111) is 0.37° [Fig. 3(d)] and 0.45° [Fig. 3(e)]. Based on Sherrer formula, the grain
Fig. 2. Raman spectra of Si film after Ni induced crystallization under different temperature for 3 h (a)a-Si:H(b)400 °C(c) 500 °C(d)600 °C(e)700 °C.
Y. Zang et al. / Materials Letters 188 (2017) 409–412
411
Fig. 3. XRD results of ɑ-Si film and c-Si film after Ni induced crystallization under different temperature for 3 h (a)a-Si:H(b)400 °C(c) 500 °C(d)600 °C(e)700 °C.
size of o111 4 orientation is calculated as 21.92 nm [Fig. 3(d)] and 18.01 nm [Fig. 3(e)]. This implies the Si film annealed at 600 °C have larger grain size than Si film annealed at 700 °C, which is corresponded to Raman results. The cross-sectional low magnification TEM morphology of Si film after Ni induced crystallization at 600 °C on 6H-SiC is shown in Fig. 4(a). The sharp interface between the Si film and the 6H-SiC substrate is clearly observed. The Si film has low surface roughness with a thickness of 0.4 mm. The selected area electron diffraction patterns of the Si film after Ni induced crystallization is shown in Fig. 4(b). It is indicated that the films is polycrystalline structure with a lattice constant of 5.43 Å, which are consistent with Si. Meanwhile, the characteristics of monocrystalline diffraction are also observed in Fig. 4(b), which shows that the Si films have high crystallization quality. High-resolution TEM images of Si films [Fig. 4(c)] show that the Si film has the cubic structure with a crystal plane spacing of 3.24 Å, which belongs to the Si(111) planes. the Si films have epitaxial connection with the 6H-SiC at local locations, as shown in Fig. 4(d). However, the preferred orientations of the Si films are not identical, which demonstrates that the Si films have a polycrystalline structure, which is in
accordance with the XRD and SAED conclusions.
4. Conclusions In this article, amorphous Si films were prepared on 6H-SiC (0001) by PECVD and induced to be crystalline structure at 400 °C 700 °C by Ni to form c-Si/6H-SiC heterojunction. The effect of the induced annealing process temperature is investigated. ɑ-Si films on 6H-SiC transforms to c-Si after 600 °C induced annealing and the Si films with o111 4 and o110 4 preferred orientations have larger grain size. The c-Si films are polycrystalline structure with a lattice constant of 5.43 Å, which are consistent with c-Si. It is demonstrated that Ni significantly promote the crystallization of the ɑ-Si films on 6H-SiC at low temperature.
Acknowledgement This work is financially supported by the the National Natural Science Foundation of China (Grant No. 51402230, 51677149),
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Y. Zang et al. / Materials Letters 188 (2017) 409–412
Fig. 4. Cross-sectional low magnification TEM image (a) and the SAED patterns (b) of the Si film after Ni induced crystallization at 600 °C on 6H-SiC, high-resolution TEM images of the Si films (c) and Si/6H-SiC interface (d) The processed HRTEM images by using FFT and Fourier mask filtering technique are shown in the insets.
Scientific Research Program Funded by Shaanxi Provincial Education Department (Grant No.14JK1302) and Natural Science Basic Research Plan in Shaanxi Province of China (Grant No.2015JM6282).
References [1] Yuan Zang, Zhiming Chen, Lianbi Li, Shunfeng Zhao, The preparation and optoelectronic characteristics of the p-n Si/SiC heterojunction, EDSSC (2009) 306–309. [2] I.V. Kityk, M. Makowska-Janusik, A. Kassiba, K.J. Plucinski, SiC nanocrystals embedded in oligoetheracrylate photopolymer matrices; new promising nonlinear optical materials, Opt. Mater. 13 (2000) 449–453. [3] L.B. Li, Z.M. Chen, Y. Zang, Epitaxial growth of Si/SiC heterostructures with different preferred orientations on 6H-SiC(0001) by LPCVD, CrystEngComm 18 (2016) 5681–5685. [4] L.B. Li, Z.M. Chen, Y. Zang, S. Feng, Atomic-scale characterization of Si(110)/6HSiC(0001) heterostructure by HRTEM, Mater. Lett. 163 (2016) 47–50. [5] L.B. Li, Z.M. Chen, Y. Zang, Interface-structure of the Si/SiC heterojunction grown on 6H-SiC, J. Appl. Phys. 117 (2015) 013104. [6] C. Long, S.A. Ustin, W. Ho, Structural defects in 3C–SiC grown on Si by
supersonic jet epitaxy, J. Appl. Phys. 86 (1999) 2509–2515. [7] A.M. AI-Dhaftri, H.A. Naseem, Metal induced crystallization (MIC) of a-Si produced by magnetron sputtering, IEEE (2005) 1516–1519. [8] Kim Joondong, A. Anderson Wayne, Metal silicide-mediated microcrystalline silicon thin-film growth for photovoltaics, Sol. Energy Mater. Sol. C 91 (2007) 534–538. [9] J.A. Schmidt, N. Budinia, Large-grained oriented polycrystalline silicon thin films prepared by nickel-silicide-induced crystallization, J. Cryst. Growth 311 (2008) 54–58. [10] Jin Jang, Jae Young Oh, Sung Ki Kim, Young Jin Choi, Soo Young Yoon, Chae Ok Kim, Electric-field-enhanced crystallization of amorphous silicon, Nature 95 (1998) 481–483. [11] Shanglong Peng, Xiaoyan Shen, Zeguo Tang, Au-induced crystallization of hydrogenated amorphous Si1 xGex(0.2 r xr 1) thin films with chemical source at low temperature, Mater. Chem. Phys. 15 (2008) 431–434. [12] Y. Kudo Kawazu, S. H. Onari, T. Arai, Initiat stage of the interfacial reaction between nickel and hydrogenated amorphous silicon, Jpn. J. Appl. Phys. 29 (1990) 729–738. [13] Shanglong Peng, Na Feng, Polycrystalline silicon thin films prepared by Ni silicide induced crystallization and the dopant effects on the crystallization, Curr. Appl. Phys. 12 (2012) 1470–1475. [14] Zang Yuan, Lianbi Li, Zhanqiang Ren, Cao Ling, zhang yan, Characterization of AlN thin film prepared by reactive sputtering, Surf. Interface Anal. 10 (2016) 1029–1032.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Si/SiC heterojunction prepared by metal induced crystallization of amorphous silicon Yuan Zang a, Lian-bi Li b,n, Jing An a, Lei Huang a, Hai Li Jin c a
Department of Electronic Engineering, Xi’an University of Technology, Xi’an 710048, China School of Science, Xi’an Polytechnic University, Xi’an 710048, China c Colloge of stomatology, Xi’an Jiaotong University, Xi’an 710004, China b
art ic l e i nf o
a b s t r a c t
Article history: Received 21 September 2016 Received in revised form 19 November 2016 Accepted 22 November 2016 Available online 29 November 2016
In this work, amorphous Si films were prepared on 6H-SiC(0001) by PECVD and induced to be crystalline structure at 400 °C 700 °C by Ni to form c-Si/6H-SiC heterojunction. Raman and XRD results indicated that ɑ-Si films on 6H-SiC transforms to c-Si after 600 °C induced annealing, and the Si films with o 111 4 and o110 4 preferred orientations have larger grain size and higher crystalline quality. TEM results indicated the c-Si films are polycrystalline structure with a lattice constant of 5.43 Å, which are consistent with c-Si. It was demonstrated that Ni promotes the crystallization of the ɑ-Si films on 6H-SiC at low temperature significantly. & 2016 Elsevier B.V. All rights reserved.
Keywords: Si/SiC heterostructure Metal induced crystallization Raman spectra TEM
1. Introduction
2. Experiments
Silicon carbide (SiC) is an excellent material candidate for power devices due to its outstanding physical properties [1]. However, with the wide bandgap, SiC-based photoelectric devices can be only driven by ultraviolet (UV) light [2]. In order to expand SiC applications, Si/SiC heterojunction is suggested to make SiCbased devices to be light-activated by non-UV lights [3]. In our previous work, the Si/SiC heterojunctions with high growth temperatures were prepared on 6H-SiC (0001) C-face [4]. Nevertheless, structural defects caused by the lattice mismatch between Si/SiC heterojunction have a serious impact on the performance of the Si/SiC photodiode [5,6]. It is reported metal induced crystallization (MIC) of amorphous Si (ɑ-Si) can decrease the growth temperature and improve the crystallization of Si film [5,6]. Schmidt [7] and jin [8] reported a Silicon Thin Films Prepared by MIC method. Peng [9] reported a Au-induced amorphous Si1 xGex films at 400 °C. However, the MIC of the Si/SiC heterostructure is rarely reported. In this work, the ɑ-Si films has been prepared on 6H-SiC(0001) and induced to be crystallized structure by Ni to form c-Si/6H-SiC heterojunction. The crystallization characteristics of samples are investigated in details. It is revealed that Ni significantly promotes the crystallization of the ɑ-Si films on 6H-SiC at low temperature.
An n-type doped (doping concentration of 1017 cm 3) 6H-SiC wafer with a thickness of 300 mm was purchased from II-VI Inc.. Prior to the preparation of PECVD process, the 6H-SiC substrates were cleaned using the standard RCA method. The ɑ-Si films were prepared at 50 °C 300 °C with a growth pressure of 80 Pa for 45 min. Gas source used in this work was Silane (10%, dilute by H2). After the ɑ-Si growth, Ni films were sputtered on ɑ-Si films by RF magnetron sputtering at room temperature with RF power of 100 W for 15 min. And the ɑ-Si films were induced crystallization by Ni metal films at 400 °C 700 °C for 3 h. Infrared absorption spectrum (Shimadzu, FTIR-8400), X-ray diffraction (Shimadzu, XRD-7000), Raman spectrum (Renishaw inVia), transmission electron microscopy (TEM, JEM-3010) were employed to characterize the Si/SiC heterostructures.
n
Corresponding author. E-mail address: [email protected] (L.-b. Li).
http://dx.doi.org/10.1016/j.matlet.2016.11.079 0167-577X/& 2016 Elsevier B.V. All rights reserved.
3. Result and discussion Infrared absorption spectrum is introduced to discuss the different configuration of Si-H bond in ɑ-Si. Fig. 1 shows infrared absorption spectrum with growth temperatures of 65 °C 300 °C. There is only one absorption peak locates at 2090 cm 1, which belongs to the stretching vibration of H-Si-H bond [10]. As temperature increases from 65 °C to 300 °C, the absorption peak decreases accordingly. This demonstrates the content of hydrogen in ɑ-Si decreases.
410
Y. Zang et al. / Materials Letters 188 (2017) 409–412
Fig. 1. Infrared absorption spectrum ofɑ-Si films prepared under different substrate temperature.
Raman spectra of Si films before and after Ni induced crystallization under different temperaturesare shown in Fig. 2. The broad and weak peaks observed near 480 cm 1 can be assigned to the ɑ-Si TO mode[11]. After 500 °C annealing, the Raman peak of the Si films shift to 500 cm 1. The peak was decomposed two peaks located at 480 cm 1 and 500 cm 1, which correspond to ɑ-
Si and intermediate Si. As annealing temperature increases to 600 °C and 700 °C, the Raman peak belong to c-Si at 520 cm 1 appears. This demonstrates that the ɑ-Si transforms to c-Si as the annealing temperature increases continuously. In Fig. 2(d), the Raman peak at 515 cm 1 can be decomposed to two peaks at 480 cm 1 and 515 cm 1, which corresponded to ɑ-Si and c-Si TO mode. The full width at half maximum (FWHM) values of the Raman peak at 515 cm 1 is 6.87. In Fig. 2(e), the FWHM values of the Raman peak at 517 cm 1 is 9.22, which is higher than the FWHM values annealed at 600 °C. This results indicate Si films with 600 °C annealing have larger grain size and higher crystalline quality. The Raman peak of c-Si (517 cm 1) was lower than the actual Si-Si bulk TO mode (520 cm 1) [12], which indicates ɑ-Si is not entirely induced to c-Si. The intensity of the Raman peak increases with increasing annealing temperatures due to improvements in the structural order [13]. The XRD patterns of the Si films after Ni induced crystallization under different annealing temperature were shown in Fig. 3. As temperature increases to 500 °C, the XRD peak at 2θ ¼28.5° [Si (111)] appears. Fig. 3(d) and Fig. 3(e) show XRD patterns with annealing temperature of 600 °C and 700 °C. There are three XRD peaks at 2θ ¼ 28.5°, 47.3° and 56.1°, which are corresponding to Si (111), Si (220) and Si (311), respectively. It is shown that ɑ-Si is induced to polycrystalline structure by Ni catalysis. Because of the lowest free energy than other directions, (111)peak is dominating in Fig. 3(d) and Fig. 3(e)[14]. The FWHM values of Si(111) is 0.37° [Fig. 3(d)] and 0.45° [Fig. 3(e)]. Based on Sherrer formula, the grain
Fig. 2. Raman spectra of Si film after Ni induced crystallization under different temperature for 3 h (a)a-Si:H(b)400 °C(c) 500 °C(d)600 °C(e)700 °C.
Y. Zang et al. / Materials Letters 188 (2017) 409–412
411
Fig. 3. XRD results of ɑ-Si film and c-Si film after Ni induced crystallization under different temperature for 3 h (a)a-Si:H(b)400 °C(c) 500 °C(d)600 °C(e)700 °C.
size of o111 4 orientation is calculated as 21.92 nm [Fig. 3(d)] and 18.01 nm [Fig. 3(e)]. This implies the Si film annealed at 600 °C have larger grain size than Si film annealed at 700 °C, which is corresponded to Raman results. The cross-sectional low magnification TEM morphology of Si film after Ni induced crystallization at 600 °C on 6H-SiC is shown in Fig. 4(a). The sharp interface between the Si film and the 6H-SiC substrate is clearly observed. The Si film has low surface roughness with a thickness of 0.4 mm. The selected area electron diffraction patterns of the Si film after Ni induced crystallization is shown in Fig. 4(b). It is indicated that the films is polycrystalline structure with a lattice constant of 5.43 Å, which are consistent with Si. Meanwhile, the characteristics of monocrystalline diffraction are also observed in Fig. 4(b), which shows that the Si films have high crystallization quality. High-resolution TEM images of Si films [Fig. 4(c)] show that the Si film has the cubic structure with a crystal plane spacing of 3.24 Å, which belongs to the Si(111) planes. the Si films have epitaxial connection with the 6H-SiC at local locations, as shown in Fig. 4(d). However, the preferred orientations of the Si films are not identical, which demonstrates that the Si films have a polycrystalline structure, which is in
accordance with the XRD and SAED conclusions.
4. Conclusions In this article, amorphous Si films were prepared on 6H-SiC (0001) by PECVD and induced to be crystalline structure at 400 °C 700 °C by Ni to form c-Si/6H-SiC heterojunction. The effect of the induced annealing process temperature is investigated. ɑ-Si films on 6H-SiC transforms to c-Si after 600 °C induced annealing and the Si films with o111 4 and o110 4 preferred orientations have larger grain size. The c-Si films are polycrystalline structure with a lattice constant of 5.43 Å, which are consistent with c-Si. It is demonstrated that Ni significantly promote the crystallization of the ɑ-Si films on 6H-SiC at low temperature.
Acknowledgement This work is financially supported by the the National Natural Science Foundation of China (Grant No. 51402230, 51677149),
412
Y. Zang et al. / Materials Letters 188 (2017) 409–412
Fig. 4. Cross-sectional low magnification TEM image (a) and the SAED patterns (b) of the Si film after Ni induced crystallization at 600 °C on 6H-SiC, high-resolution TEM images of the Si films (c) and Si/6H-SiC interface (d) The processed HRTEM images by using FFT and Fourier mask filtering technique are shown in the insets.
Scientific Research Program Funded by Shaanxi Provincial Education Department (Grant No.14JK1302) and Natural Science Basic Research Plan in Shaanxi Province of China (Grant No.2015JM6282).
References [1] Yuan Zang, Zhiming Chen, Lianbi Li, Shunfeng Zhao, The preparation and optoelectronic characteristics of the p-n Si/SiC heterojunction, EDSSC (2009) 306–309. [2] I.V. Kityk, M. Makowska-Janusik, A. Kassiba, K.J. Plucinski, SiC nanocrystals embedded in oligoetheracrylate photopolymer matrices; new promising nonlinear optical materials, Opt. Mater. 13 (2000) 449–453. [3] L.B. Li, Z.M. Chen, Y. Zang, Epitaxial growth of Si/SiC heterostructures with different preferred orientations on 6H-SiC(0001) by LPCVD, CrystEngComm 18 (2016) 5681–5685. [4] L.B. Li, Z.M. Chen, Y. Zang, S. Feng, Atomic-scale characterization of Si(110)/6HSiC(0001) heterostructure by HRTEM, Mater. Lett. 163 (2016) 47–50. [5] L.B. Li, Z.M. Chen, Y. Zang, Interface-structure of the Si/SiC heterojunction grown on 6H-SiC, J. Appl. Phys. 117 (2015) 013104. [6] C. Long, S.A. Ustin, W. Ho, Structural defects in 3C–SiC grown on Si by
supersonic jet epitaxy, J. Appl. Phys. 86 (1999) 2509–2515. [7] A.M. AI-Dhaftri, H.A. Naseem, Metal induced crystallization (MIC) of a-Si produced by magnetron sputtering, IEEE (2005) 1516–1519. [8] Kim Joondong, A. Anderson Wayne, Metal silicide-mediated microcrystalline silicon thin-film growth for photovoltaics, Sol. Energy Mater. Sol. C 91 (2007) 534–538. [9] J.A. Schmidt, N. Budinia, Large-grained oriented polycrystalline silicon thin films prepared by nickel-silicide-induced crystallization, J. Cryst. Growth 311 (2008) 54–58. [10] Jin Jang, Jae Young Oh, Sung Ki Kim, Young Jin Choi, Soo Young Yoon, Chae Ok Kim, Electric-field-enhanced crystallization of amorphous silicon, Nature 95 (1998) 481–483. [11] Shanglong Peng, Xiaoyan Shen, Zeguo Tang, Au-induced crystallization of hydrogenated amorphous Si1 xGex(0.2 r xr 1) thin films with chemical source at low temperature, Mater. Chem. Phys. 15 (2008) 431–434. [12] Y. Kudo Kawazu, S. H. Onari, T. Arai, Initiat stage of the interfacial reaction between nickel and hydrogenated amorphous silicon, Jpn. J. Appl. Phys. 29 (1990) 729–738. [13] Shanglong Peng, Na Feng, Polycrystalline silicon thin films prepared by Ni silicide induced crystallization and the dopant effects on the crystallization, Curr. Appl. Phys. 12 (2012) 1470–1475. [14] Zang Yuan, Lianbi Li, Zhanqiang Ren, Cao Ling, zhang yan, Characterization of AlN thin film prepared by reactive sputtering, Surf. Interface Anal. 10 (2016) 1029–1032.