Abstract
Objective: Herein, we report the effect of variation of hydrogen flow rate on the properties of Si:H films synthesized using PE-CVD method. Raman spectroscopy analysis show an increase in crystalline volume fraction and crystallite size implying that hydrogen flow in PE-CVD promotes the growth of crystallinity in nc-Si:H films with an expense of a reduction in deposition rate.
Methods: FTIR spectroscopy analysis indicates that hydrogen content in the film increases with an increase in hydrogen flow rate and hydrogen is predominantly incorporated in Si-H2 and (Si-H2)n bonding configuration. The optical band gap determined using E04 method and Tauc method (ETauc) show an increasing trend with an increase in hydrogen flow rate and E04 is found higher than ETauc over the entire range of hydrogen flow rate studied.
Results and Conclusion: We found that the defect density and Urbach energy increases with an increase in hydrogen flow rate. Photosensitivity (σPhoto /σDark) decreases from ∼103 to ∼1 when hydrogen flow rate is increased from 30 sccm to 100 sccm and can be attributed to amorphous-to-nanocrystallization transition in Si:H films. The results obtained from the present study demonstrated that hydrogen flow rate is an important deposition parameter in PECVD to synthesize nc-Si:H films.
Keywords: Amorphous-to-nanocrystalline transition, Raman Scattering, FTIR spectroscopy, UV-Visible spectroscopy, Electrical properties, silicon thin films.
Graphical Abstract
[1]
Mukhopadhyay S, Chowdhury A, Ray S. Nanocrystalline silicon: A material for thin film solar cells with better stability. Thin Solid Films 2008; 516: 6824-8.
[http://dx.doi.org/10.1016/j.tsf.2007.12.065]
[http://dx.doi.org/10.1016/j.tsf.2007.12.065]
[2]
Yang J, Yan B, Guha S. Amorphous and nanocrystalline silicon-based multi-junction solar cells. Thin Solid Films 2005; 487: 162-9.
[http://dx.doi.org/10.1016/j.tsf.2005.01.058]
[http://dx.doi.org/10.1016/j.tsf.2005.01.058]
[3]
Zhang L, Shen L, Jiang F, Qian B, Han Z, Hou H. Influence of annealing temperature on the properties of polycrystalline silicon films formed by rapid thermal annealing of a-Si:H films. J Mater Sci Mater Electron 2013; 24: 4209-12.
[http://dx.doi.org/10.1007/s10854-013-1386-9]
[http://dx.doi.org/10.1007/s10854-013-1386-9]
[4]
Adikaari A, Mudugamuwa N, Silva S. Nanocrystalline silicon solar cells from excimer laser crystallization of amorphous silicon. Sol Energy Mater Sol Cells 2008; 92: 634-8.
[http://dx.doi.org/10.1016/j.solmat.2008.01.011]
[http://dx.doi.org/10.1016/j.solmat.2008.01.011]
[5]
Shim J, Im S, Kim Y, Cho N. Nanostructural and optical features of hydrogenated nanocrystalline silicon films prepared by aluminium-induced crystallization. Thin Solid Films 2006; 503: 55-9.
[http://dx.doi.org/10.1016/j.tsf.2005.11.114]
[http://dx.doi.org/10.1016/j.tsf.2005.11.114]
[6]
Goh B, Wah C, Aspanut Z, Rahman S. Structural and optical properties of nc-Si:H thin films deposited by layer-by-layer technique. J Mater Sci Mater Electron 2014; 25: 286-96.
[http://dx.doi.org/10.1007/s10854-013-1584-5]
[http://dx.doi.org/10.1007/s10854-013-1584-5]
[7]
Lee S, Park Y. Highly-conductive B-doped nc-Si:H thin films deposited at room temperature by using SLAN ECR-PECVD. J Korean Phys Soc 2014; 65: 651-6.
[http://dx.doi.org/10.3938/jkps.65.651]
[http://dx.doi.org/10.3938/jkps.65.651]
[8]
Bakr N, Funde A, Waman V, et al. Influence of deposition pressure on structural, optical and electrical properties of nc-Si: H films deposited by HW-CVD. J Phys Chem Solids 2011; 72: 685-91.
[http://dx.doi.org/10.1016/j.jpcs.2011.02.019]
[http://dx.doi.org/10.1016/j.jpcs.2011.02.019]
[9]
He H, Ye C, Wang X, Huang F, Liua Y. Effect of driving frequency on growth and structure of silicon films deposited by radio-frequency and very-high-frequency magnetron sputtering. ECS J Solid State Sci Technol 2014; 3(5): Q74-8.
[http://dx.doi.org/10.1149/2.008405jss]
[http://dx.doi.org/10.1149/2.008405jss]
[10]
Peng S, Wang D, Yang F, Wang Z, Ma F. Grown low-temperature microcrystalline silicon thin film by VHF PECVD for thin films solar cell. J Nanomater 2015; Article ID 327596:1-5.
[11]
Gope J, Kumar S, Singh S, Rauthan C, Srivastava P. Silicon and Energy. Silicon 2012; 4: 127-35.
[http://dx.doi.org/10.1007/s12633-012-9109-z]
[http://dx.doi.org/10.1007/s12633-012-9109-z]
[12]
Parashar A, Kumar S, Gope J, Rauthan C, Hashmi S, Dixit P. RF power density dependent phase formation in hydrogenated silicon films. J Non-Cryst Solids 2010; 356: 1774-8.
[http://dx.doi.org/10.1016/j.jnoncrysol.2010.07.019]
[http://dx.doi.org/10.1016/j.jnoncrysol.2010.07.019]
[13]
Gope J, Kumar S, Sudhakar S, Rauthan C, Srivastava P. Effect of silane flow rate on structural, electrical and optical properties of silicon thin films grown by VHF PECVD technique. Mater Chem Phys 2013; 141: 89-94.
[http://dx.doi.org/10.1016/j.matchemphys.2013.04.028]
[http://dx.doi.org/10.1016/j.matchemphys.2013.04.028]
[14]
Hadjadj A, Beorchia A, Cabarrocas P, Boufendi L, Huet S, Bubendorff J. Effects of the substrate temperature on the growth and properties of hydrogenated nanostructured silicon thin films. J Phys D Appl Phys 2001; 34: 690-9.
[http://dx.doi.org/10.1088/0022-3727/34/5/305]
[http://dx.doi.org/10.1088/0022-3727/34/5/305]
[15]
Chengzhao C, Shenghua Q, Cuiqin L, et al. Role of hydrogen dilution in the low-temperature growth of nanocrystalline Si:H thin films from SiH4/H2 mixture. Plasma Sci Technol 2009; 11: 297-301.
[http://dx.doi.org/10.1088/1009-0630/11/3/10]
[http://dx.doi.org/10.1088/1009-0630/11/3/10]
[16]
Chowdhury A, Mukhopadhyay S, Ray S. Effect of electrode separation on PECVD deposited nanocrystalline silicon thin film and solar cell properties. Sol Energy Mater Sol Cells 2010; 94: 1522-7.
[http://dx.doi.org/10.1016/j.solmat.2010.01.017]
[http://dx.doi.org/10.1016/j.solmat.2010.01.017]
[17]
Knights JC, Lujan RA. Microstructure of plasma‐deposited a‐Si : H films. Appl Phys Lett 1979; 35: 244-6.
[http://dx.doi.org/10.1063/1.91086]
[http://dx.doi.org/10.1063/1.91086]
[18]
Stoffels E, Stoffels WW, Koresen GMW, de Hoog FJ. Dust formation and charging in an Ar/SiH4 radio‐frequency discharge. J Vac Sci Technol A 1996; 14: 556-61.
[http://dx.doi.org/10.1116/1.580144]
[http://dx.doi.org/10.1116/1.580144]
[20]
Das D, Jana M, Barua AK. Heterogeneity in microcrystalline-transition state: Origin of Si-nucleation and microcrystallization at higher rf power from Ar-diluted SiH4 plasma. J Appl Phys 2001; 89: 3041.
[http://dx.doi.org/10.1063/1.1345852]
[http://dx.doi.org/10.1063/1.1345852]
[21]
Matsuda A. Formation kinetics and control of microcrystallite in μc-Si:H from glow discharge plasma. J Non-Cryst Solids 1983; 59-60: 767-74.
[http://dx.doi.org/10.1016/0022-3093(83)90284-3]
[http://dx.doi.org/10.1016/0022-3093(83)90284-3]
[22]
Lee S, Heo D, Kang J, Park Y, Rhee S. Microcrystalline silicon film deposition from H 2 - He - SiH4 using remote plasma enhanced chemical vapor deposition. J Electrochem Soc 1998; 145: 2900-4.
[http://dx.doi.org/10.1149/1.1838733]
[http://dx.doi.org/10.1149/1.1838733]
[23]
Fontcuberta MA, Brenot R, Hamers EAG, Vanderhaghen R, Cabarrocas PR. In situ investigation of polymorphous silicon deposition. J Non-Cryst Solids 2000; 266-269: 48-53.
[http://dx.doi.org/10.1016/S0022-3093(99)00723-1]
[http://dx.doi.org/10.1016/S0022-3093(99)00723-1]
[24]
Carabe J, Gandia J, Gonzalez N, Guitierrez M. Microstructure of thin films prepared by plasma-enhanced chemical vapour deposition of helium-diluted silane. Appl Surf Sci 1999; 143: 11-5.
[http://dx.doi.org/10.1016/S0169-4332(99)00086-0]
[http://dx.doi.org/10.1016/S0169-4332(99)00086-0]
[25]
Bhattacharya K, Das D. Nanocrystalline silicon prepared at high growth rate using helium dilution. Bull Mater Sci 2008; 31(3): 467.
[http://dx.doi.org/10.1007/s12034-008-0073-6]
[http://dx.doi.org/10.1007/s12034-008-0073-6]
[26]
Matsuda A, Mashima S, Hasezaki K, Suzuki A, Yamasaki S, McElheny PJ. Preparation of stable and photoconductive hydrogenated amorphous silicon from a Xe‐diluted silane plasma. Appl Phys Lett 1991; 58: 2494-6.
[http://dx.doi.org/10.1063/1.104854]
[http://dx.doi.org/10.1063/1.104854]
[27]
Jadhavar A, Pawbake A, Waykar R, et al. Influence of RF power on structural optical and electrical properties of hydrogenated nano-crystalline silicon (nc-Si:H) thin films deposited by PE-CVD. J Mater Sci Mater Electron 2016; 27(12): 12365-73.
[http://dx.doi.org/10.1007/s10854-016-5024-1]
[http://dx.doi.org/10.1007/s10854-016-5024-1]
[28]
Brodsky M, Cardona M, Cuomo JJ. Infrared and Raman spectra of the silicon-hydrogen bonds in amorphous silicon prepared by glow discharge and sputtering. Phys Rev B 1977; 16: 3556.
[http://dx.doi.org/10.1103/PhysRevB.16.3556]
[http://dx.doi.org/10.1103/PhysRevB.16.3556]
[29]
Swanepoel R. Determination of the thickness and optical constants of amorphous silicon. J Phys E Sci Instrum 1983; 16: 1214-22.
[http://dx.doi.org/10.1088/0022-3735/16/12/023]
[http://dx.doi.org/10.1088/0022-3735/16/12/023]
[30]
Matsuda A. Thin film silicon-Growth process and solar cell application. Jpn J Appl Phys 2004; 43(12): 7909-20.
[http://dx.doi.org/10.1143/JJAP.43.7909]
[http://dx.doi.org/10.1143/JJAP.43.7909]
[31]
Chen W, Cariou R, Hamon G, et al. Influence of deposition rate on the structural properties of plasma-enhanced CVD epitaxial silicon. Sci Rep 2017; 7: 43968-8.
[http://dx.doi.org/10.1038/srep43968 ] [PMID: 28262840]
[http://dx.doi.org/10.1038/srep43968 ] [PMID: 28262840]
[32]
Gani M, Rahman S. Effects of hydrogen dilution on CNx film properties deposited using rf PECVD from a mixture of ethane, nitrogen and hydrogen. Mater Chem Phys 2014; 144: 377-84.
[http://dx.doi.org/10.1016/j.matchemphys.2014.01.005]
[http://dx.doi.org/10.1016/j.matchemphys.2014.01.005]
[33]
Marquardt D. An Algorithm for Least-Squares Estimation of Nonlinear Parameters. J Soc Ind Appl Math 1963; 11(2): 431.
[http://dx.doi.org/10.1137/0111030]
[http://dx.doi.org/10.1137/0111030]
[34]
Kaneko T, Wakagi M, Onisawa K, Minemura T. Change in crystalline morphologies of polycrystalline silicon films prepared by radio‐frequency plasma‐enhanced chemical vapor deposition using SiF4+H2 gas mixture at 350 °C. Appl Phys Lett 1994; 64: 1865.
[http://dx.doi.org/10.1063/1.111781]
[http://dx.doi.org/10.1063/1.111781]
[35]
He Y, Yin C, Cheng G, Wang L, Liu X, Hu GY. The structure and properties of nanosize crystalline silicon films. J Appl Phys 1994; 75: 797.
[http://dx.doi.org/10.1063/1.356432]
[http://dx.doi.org/10.1063/1.356432]
[36]
He J, Guo A, Li W, et al. Structural and optoelectronic properties of a-Si:H:A new analysis based on spectroscopic ellipsometry. Vacuum 2017; 146: 409-21.
[37]
Samanta S, Das D. Nanocrystalline silicon thin films from SiH4 plasma diluted by H2 and He in RF-PECVD. J Phys Chem Solids 2017; 105: 90-8.
[http://dx.doi.org/10.1016/j.jpcs.2017.02.013]
[http://dx.doi.org/10.1016/j.jpcs.2017.02.013]
[38]
Feenstra KF. Hot-wire chemical vapour deposition of amorphous silicon and the application in solar cells PhD thesis Utrecht University the Netherlands 1998.
[39]
Saha SC, Barua AK, Ray S. The role of hydrogen dilution and radio frequency power in the formation of microcrystallinity of n‐type Si:H thin film. J Appl Phys 1993; 74(9): 5561.
[http://dx.doi.org/10.1063/1.354216]
[http://dx.doi.org/10.1063/1.354216]
[40]
Lucovsky G. Vibrational spectroscopy of hydrogenated amorphous silicon alloys. Solar Cells 1980; 2: 431-42.
[http://dx.doi.org/10.1016/0379-6787(80)90019-8]
[http://dx.doi.org/10.1016/0379-6787(80)90019-8]
[41]
Knights JC, Lucovsky G, Nemanich RJ. Defects in plasma-deposited a-Si: H. J Non-Cryst Solids 1979; 32: 393.
[http://dx.doi.org/10.1016/0022-3093(79)90084-X]
[http://dx.doi.org/10.1016/0022-3093(79)90084-X]
[42]
Montero I, Galán L, Najmi O, Albella JM. Disorder-induced vibration-mode coupling in SiO2 films observed under normal-incidence infrared radiation. Phys Rev B Condens Matter 1994; 50(7): 4881-4.
[http://dx.doi.org/10.1103/PhysRevB.50.4881 PMID: 9976802]
[http://dx.doi.org/10.1103/PhysRevB.50.4881 PMID: 9976802]
[43]
Halindintwali S, Knoesen D, Swanepoel R, et al. Improved stability of intrinsic nanocrystalline Si thin films deposited by hot-wire chemical vapour deposition technique. Thin Solid Films 2007; 515: 8040.
[http://dx.doi.org/10.1016/j.tsf.2007.03.051]
[http://dx.doi.org/10.1016/j.tsf.2007.03.051]
[44]
Tsu DV, Lucovsky G, Davidson BN. Effects of the nearest neighbors and the alloy matrix on SiH stretching vibrations in the amorphous SiOr:H (0<r<2) alloy system. Phys Rev B Condens Matter 1989; 40(3): 1795-805.
[http://dx.doi.org/10.1103/PhysRevB.40.1795 ] [PMID: 9992040]
[http://dx.doi.org/10.1103/PhysRevB.40.1795 ] [PMID: 9992040]
[45]
Jones A, Ahmed W, Hassan I, et al. The impact of inert gases on the structure, properties and growth of nanocrystalline diamond. J Phys Condens Matter 2003; 15: S2969-75.
[http://dx.doi.org/10.1088/0953-8984/15/39/020]
[http://dx.doi.org/10.1088/0953-8984/15/39/020]
[46]
Shanks H, Fang C, Cardona M, Demond F, Kalbitzer S. Infrared Spectrum and Structure of Hydrogenated Amorphous Silicon. Phys Status Solidi, B Basic Res 1980; 100: 43-56.
[http://dx.doi.org/10.1002/pssb.2221000103]
[http://dx.doi.org/10.1002/pssb.2221000103]
[47]
Langford AA, Fleet ML, Nelson BP, Lanford WA, Maley N. Infrared absorption strength and hydrogen content of hydrogenated amorphous silicon. Phys Rev B Condens Matter 1992; 45(23): 13367-77.
[http://dx.doi.org/10.1103/PhysRevB.45.13367 ] [PMID: 10001420]
[http://dx.doi.org/10.1103/PhysRevB.45.13367 ] [PMID: 10001420]
[48]
Itoh T, Yananoto K, Harada H, et al. Role of hydrogen in hydrogenated microcrystalline silicon. Sol Energy Mater Sol Cells 2001; 66: 239-44.
[http://dx.doi.org/10.1016/S0927-0248(00)00179-3]
[http://dx.doi.org/10.1016/S0927-0248(00)00179-3]
[49]
Chen CZ, Qiu SH, Liu CQ, et al. Low temperature fast growth of nanocrystalline silicon films by rf-PECVD from SiH4/H2 gases: microstructural characterization. J Phys D Appl Phys 2008.41195413
[http://dx.doi.org/10.1088/0022-3727/41/19/195413]
[http://dx.doi.org/10.1088/0022-3727/41/19/195413]
[50]
Tauc J. Absorption edge and internal electric fields in amorphous semiconductors. Mater Res Bull 1970; 5: 721-9.
[http://dx.doi.org/10.1016/0025-5408(70)90112-1]
[http://dx.doi.org/10.1016/0025-5408(70)90112-1]
[51]
Cremona A, Laguardia L, Vassallo E, et al. Optical and structural properties of siliconlike films prepared by plasma-enhanced chemical-vapor deposition J Appl Phys 2005; 97: 023533(01)-.
[52]
Amor SB, Atyaoui M, Bousbih R, Haddadi I, Dimassi W, Ezzaouia H. Effect of substrate temperature on microstructure and optical properties of hydrogenated nanocrystalline Si thin films grown by plasma enhanced chemical vapor deposition. Sol Energy 2014; 108: 126-34.
[http://dx.doi.org/10.1016/j.solener.2014.06.024]
[http://dx.doi.org/10.1016/j.solener.2014.06.024]
[53]
Lucovsky G, Nemanich RJ, Knights JC. Structural interpretation of the vibrational spectra of a-Si: H alloys. Phys Rev B Condens Matter 1979; 19: 2064.
[http://dx.doi.org/10.1103/PhysRevB.19.2064]
[http://dx.doi.org/10.1103/PhysRevB.19.2064]
[54]
Saitoh T, Shimada T, Migitaka M. Preparation and properties of microcrystalline silicon films using photochemical vapor deposition. J Non-Cryst Solids 1983; 715: 59-60.
[http://dx.doi.org/10.1016/0022-3093(83)90271-5]
[http://dx.doi.org/10.1016/0022-3093(83)90271-5]
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