Electronic structure and optical properties of the scintillation material wurtzite ZnS(Ag)

Electronic structure and optical properties of the scintillation material wurtzite ZnS(Ag) 1 first-author 1 2 1 1 1 corresp Corresponding author, qzhao@ncepu.edu.cn Corresponding author, qzhao@ncepu.edu.cn qzhao@ncepu.edu.cn 1 3 4 Beijing Key Laboratory of Passive Safety Technology for Nuclear Energy, School of Nuclear Science and Engineering, North China Electric Power University, Beijing 102206, China Beijing Key Laboratory of Passive Safety Technology for Nuclear Energy, School of Nuclear Science and Engineering, North China Electric Power University, Beijing 102206, China School of Electrical and Electronic Engineering, North China Electric Power University, Beijing 102206, China School of Electrical and Electronic Engineering, North China Electric Power University, Beijing 102206, China Northwest Institute of Nuclear Technology, Xi’an 710024, China Northwest Institute of Nuclear Technology, Xi’an 710024, China School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, China School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, China In order to investigate the effect of Ag doping (ZnS(Ag)) and Zn vacancy ( V Zn ) on the alpha particle detection performance of wurtzite (WZ) ZnS as a scintillation cell component, the electronic structure and optical properties of ZnS, ZnS(Ag), and V Zn were studied by first-principles calculation based on the density functional theory (DFT). The results show that the band gaps of ZnS, ZnS(Ag), and V Zn are 2.17 eV, 1.79 eV, and 2.37 eV, respectively. Both ZnS(Ag) and V Zn enhance the absorption and reflection of the low energy photons. A specific energy, about 2.9 eV, leading to decrease of detection efficiency is observed. The results indicate that Ag-doping has a complex effect on the detection performance. It is beneficial to produce more visible light photons than pure WZ ZnS when exposed to the same amount of radiation while the increase of the absorption to visible light photons weakens the detection performance. Zn vacancy has negative effect on the detection performance. If we want to improve the detection performance of WZ ZnS, Ag-doping will be a good way, but we should reduce the absorption to visible light photons and control the number of Zn vacancy rigorously. Wurtzite ZnS Electronic structure Optical properties First-principles 1 Introduction 1 In recent years, the zinc sulfide (ZnS) crystal has been a research focus due to its attractive physical properties [ 1 1 - 4 4 1-4 ] as well as its promising device applications [ 5 5 - 12 12 5-12 ]. It has been widely used in diverse fields including semiconductors, thin film electroluminescent, sensors, and so on. Silver activated ZnS (ZnS(Ag)) has a maximum in the scintillation emission spectrum at 450 nm. The light conversion efficiency is relatively poor for fast electrons which may be an advantage when detecting heavy charged particles in a relatively intense γ -ray background [ 13 13 ]. ZnS(Ag) can also be used to detect thermal neutrons if a lithium compound enriched in 6 Li is incorporated [ 14 14 ]. Another use for ZnS(Ag) is for the detection of fast neutrons [ 15 15 ]. A fast neutron detector can be made by imbedding the ZnS(Ag) in a clear hydrogenous compound. ZnS is usually used as a scintillation cell component for the detection of the alpha particles [ 16 16 - 20 20 16-20 ]. There are two types of structures of ZnS, the wurtzite (WZ) structure and the zinc-blende (ZB) structure. There are a few researchers that made contributions to the study of WZ ZnS. Chen [ 21 21 ] et al. investigated the optical and excitonic properties of the ZnS nanowires toward efficient ultraviolet emission at room temperature. Reddy [ 22 22 ] et al. found that WZ ZnS is more desirable for optoelectronics because its luminescent properties are considerably more enhanced than sphalerite. Zeng [ 23 23 ] et al. investigated charge transfer and optical properties of wurtzite-type ZnS/(CdS/ZnS) n ( n = 2, 4, 8) superlattices. Zhang [ 24 24 ] et al. investigated the blue and green emissions of ZnS ceramics and found that the wurtzite-type ZnS ceramics could provide an interesting application in the development of novel luminescent devices. Ong [ 25 25 ] et al. determined optical constants of WZ ZnS thin films by spectroscopic ellipsometry. Zhang [ 26 26 ] et al. researched the surface states and their influence on the luminescence of ZnS nanocrystallite. Ye [ 27 27 ] et al. investigated the origin of the green photoluminescence for the ZnS. Tadashi Mitsui [ 28 28 ] et al. studied the cathodoluminescence image of defects and luminescence centers in ZnS/GaAs(100). Wang [ 29 29 ] et al. studied the photovoltaic effect of ZnS as semiconductors. However, there are few theoretical researches on the ZnS as a scintillation cell component, and many researchers [ 16 16 - 20 20 16-20 ] studied the ZnS crystal as a kind of scintillation material used for alpha particles detection through the experimental study, but they did not mention the crystal structure of the ZnS crystal. As a scintillation component, the electronic structure and optical properties are important to detective performance. In order to explain the mechanism of the scintillation luminescence in WZ ZnS, we need to know the effect of the Ag-doping, Zn vacancy on the detective performance of ZnS, and whether the WZ crystal structure is better as a kind of scintillation material. We studied the lattice constants, electronic structure, and optical properties of the pure ZnS, ZnS(Ag), and V Zn . 2 Calculation 1 The space group of WZ ZnS is P63mc(186), and the crystal structure of the perfect WZ ZnS is shown in Fig. 1(a) and (b) Fig. 1(a) and (b) . There is one zinc atom and one sulphur atom in each ZnS unit cell, in which the atomic coordinate of Zn is (0.3333, 0.6667, 0), and the atomic coordinate of S is (0.3333, 0.6667, 0.374). We applied a 2×2×1 supercell to calculating the electronic structure and optical properties of ZnS, ZnS(Ag), and V Zn . Figure 1(c) Figure 1(c) is the crystal structure of the ZnS doped with an Ag atom, noted as ZnS(Ag). Figure 1(d) Figure 1(d) shows the crystal structure of the ZnS with a Zn vacancy, noted as V Zn in this paper. The Ag doping concentration and the vacancy concentration may be a bit high, but it is reasonable to explain the effects of the Ag doping and the vacancy on the electronic structure and the optical properties of the WZ ZnS. All calculations were using the Cambridge Serial Total Energy Package (CASTEP) [ 30 30 ]. CASTEP is an ab initio quantum mechanics application software based on the DFT. It uses the plane wave pseudo-potential (PWP) method to substitute ionic potentials. The expansion of the electronic wave function is spread through the plane wave basis sets. The exchange correlation potentials among the electrons are described by the general gradient approximation (GGA) with a Perdew-Burke-Ernzerhol (PBE) form [ 31 31 ]. To ensure the calculation efficiency and accuracy, after the convergence test, we chose the kinetic cutoff energy as 400 eV for all the calculations, and the k -mesh as 4×4×4. We obtained the equilibrium crystal structure when the maximum force on all atoms was less than 0.05 eV/nm, the maximum stress of the crystal was smaller than 0.02 GPa, and the maximum change of energy per atom was 1.0× 10 -5 eV/atom. The valence electrons involved are 3 d 10 4 s 2 for Zn, 3 s 2 3 p 4 for S, and 4 d 10 5 s 1 for Ag, respectively. After we optimized the crystal structure of ZnS, ZnS(Ag), and V Zn , we calculated the electronic structure and optical properties of them. 3 Results and discussion 1 3.1 Optimization of the crystal structure 2 In order to figure out the electronic structure and optical properties of WZ ZnS, ZnS(Ag), and V Zn , we optimized those crystal structure first. Table 1 Table 1 shows the results of our calculation, the other theoretical results, and experimental data. 1 1 Crystal 1 1 ZnS Exp [ 1 1 , 38 38 ] 1 1 ZnS [ 32 32 , 39 39 ] 1 1 ZnS 1 1 ZnS(Ag) 1 1 V Zn 1 1 a (Å) 1 1 3.822 1 1 3.840 1 1 3.841 1 1 3.853 1 1 3.790 1 1 c (Å) 1 1 6.260 1 1 6.267 1 1 6.303 1 1 6.397 1 1 6.345 1 1 band gap (eV) 1 1 3.7-3.8 1 1 2.19 1 1 2.17 1 1 1.79 1 1 2.37 From Table 1 Table 1 , lattice parameters of those crystals that we calculated are consistent with the other theoretical results and experimental data. The band gap of WZ ZnS we calculated is 2.17 eV which is consistent with other theoretical values 2.19 eV [ 32 32 ], 2.06 eV [ 33 33 ], while they are smaller than the experimental data 3.7-3.8 eV [ 1 1 ] and 3.91 eV [ 34 34 ] for the WZ ZnS. The underestimation of the band gaps is mainly due to the simple form of GGA, and this is a well-known issue [ 35 35 ]. It should be noted that the density functional formalism is limited in its validity [ 36 36 ] so the band structure derived from it cannot be used directly for comparison with experiment. However, GGA is still a widely used method and has achieved many successes. Results based on GGA are generally acclaimed [ 37 37 ]. 3.2 Electronic structure 2 As a scintillation material, the electronic structure of WZ ZnS is important to its luminescence performance. When ZnS is exposed to the alpha particles radiation, photons are produced by the de-excitation of the electrons. The luminescence performance properties of scintillation materials are closely related to the electronic structure of them. The detection performance will be better with higher luminous efficiency of the visible light photons. We calculated the band structure and the electronic density of states of ZnS, ZnS(Ag) and V Zn . Figure 2 Figure 2 is the band structure of those crystals, which shows the band gaps of WZ ZnS, ZnS(Ag), and V Zn are 2.17 eV, 1.79 eV, and 2.37 eV, respectively. Compared with the pure ZnS, ZnS(Ag) changes somewhat because of the doping. The conduction band of ZnS(Ag) is similar to that of ZnS, but the top point of the valence band of ZnS(Ag) moves to a higher energy level. Both the top point of the valence band and the lowest point of the conduction band of V Zn move to a higher energy level when compared with ZnS. The top point of the valence band of V Zn is still lower than that of ZnS(Ag). In a word, the main changes occur near the Fermi level when there are Ag doping and Zn vacancy in WZ ZnS. The electrons of ZnS(Ag) need less energy to transit from the valence band to conduction band. Therefore, Ag doping can improve the detection efficiency of ZnS because it can produce more photons when exposed to the same amount nuclear radiation and their energy is in the visible light range. On the contrary, the electrons of V Zn need more energy, which means that Zn vacancy decreases the detection efficiency of ZnS. Figure 3 Figure 3 is the distribution of the total density of states (TDOS) of WZ ZnS, ZnS(Ag), and V Zn . From Fig. 3 Fig. 3 , the result of the TDOSs is in agreement with the band structure. In the low valence band (-13 eV–11 eV), no changes occur. The lowest point of the conduction band changes somewhat in ZnS(Ag) and V Zn . Those results can explain the difference of the band gaps. Figure 4 Figure 4 shows the TDOS and the partial density of states (PDOS) of WZ ZnS. The low valence band of ZnS is composed by the s state electrons of S, and the high valence band is mainly composed by the d state electrons of Zn and p states electrons of S. The forming of the conduction band is the contribution of the s state electrons of Zn and the p state electrons of S. Figure 5 Figure 5 shows the TDOS and PDOSs of ZnS(Ag). The top point of the valence band of ZnS(Ag) moves to a higher energy level, and the lowest point of the conduction band doesn’t change. The s state electrons of Ag make some contribution to the high valence band, the d state electrons of Ag make some contribution to the conduction band, and the result is the band gap becomes smaller than that of pure ZnS. Compared with the pure ZnS crystal, Ag doping could produce more visible light photons when ZnS(Ag) is exposed to the the same amount of radiation. Figure 6 Figure 6 shows the TDOS and PDOSs of V Zn . Both the top point of the valence band and the lowest point of the conduction band of V Zn move to a higher energy level when compared with WZ ZnS. The band gap of V Zn is bigger that of ZnS, which means electrons need more energy to transit from the valence band to the conduction band. This result decreases the detection efficiency. Therefore, reducing Zn vacancies is beneficial to improving the detective performance of ZnS. 3.3 Optical properties 2 In the linear response range, the optical response function of a crystal can usually be described by a dielectric function in a complex number form ε ( ω ) = ε 1 ( ω ) + i ε 2 ( ω ), from which we can easily get the spectrum information. The imaginary part, ε 2 ( ω ), represents absorption characteristic well, and it is associated electronic structure. We calculated ε 2 ( ω ) according to the definition of direct probability transition. Figure 7 Figure 7 shows ε 2 ( ω ) of WZ ZnS, ZnS(Ag), and V Zn , respectively. In the high energy range (5 eV - 10 eV), the change isn’t obvious. In the low energy, about 1.5 eV, there are two peaks belonging to ZnS(Ag) and V Zn , respectively. Those changes indicates that Ag doping and Zn vacancy can enhance the absorption of the ZnS crystal to the low energy photons, and it has a negative effect on the detection efficiency of ZnS(Ag) and V Zn . Figure 8 Figure 8 shows the absorption spectra of ZnS, ZnS(Ag), and V Zn . Obviously, Ag doping and Zn vacancy could increase the absorption of low energy photons whose energy is in the visible light range. V Zn absorbs more photons than ZnS(Ag) at the same energy. Figure 9 Figure 9 shows the reflection coefficient of WZ ZnS, ZnS(Ag), and V Zn . In the low energy range, around 1.8 eV, we can observe two peaks belonging to ZnS(Ag) and V Zn , respectively. They are beneficial to detective performance. Valleys appears around the 2.9 eV where the reflection coefficients of ZnS(Ag) and V Zn are smaller than the perfect ZnS. The valleys would weaken the detection efficiency. In short, a red-shift can be observed in the Fig. 9 Fig. 9 . Ag doping and Zn vacancy increase the reflection coefficient of the low energy photons. A higher reflection coefficient of the low energy photons can improve the detection efficiency of ZnS. 4 Summary 1 In order to investigate the effect of Ag doping and Zn vacancy on the detective performance of WZ ZnS as a scintillation cell component, we calculated the electronic structure and optical properties of ZnS, ZnS(Ag), and V Zn by using the first-principles method based on the DFT. The results of our calculation are as follows: (1) The band gaps of WZ ZnS, ZnS(Ag), and V Zn are 2.17 eV, 1.79 eV, and 2.37 eV, respectively. It shows that electrons of ZnS(Ag) need less energy, and electrons of V Zn need more energy than ZnS, to transit from the valence band to conduction band when they are exposed to the same amount of radiation. (2) The density of states show that the top point of the valence band of ZnS(Ag) moves to a higher energy level, the lowest point of the conduction band doesn’t change, and the result is the band gap becomes smaller than pure WZ ZnS. Both the top point of the valence band and the lowest point of the conduction band of V Zn moves to a higher energy level, when compared with pure ZnS. (3) Ag-doping and Zn vacancy enhance the absorption of the low energy photons, especially in V Zn . Reflection coefficient of ZnS(Ag) and V Zn perform higher than ZnS in the visible light range. Meanwhile, a specific energy, about 2.9 eV, leading to decrease of detection efficiency is observed, which needs to be avoided. The results indicate that Ag-doping has a complex effect on the detection performance. It is beneficial to produce more visible light photons than pure WZ ZnS when exposed to the same amount of radiation, because the increase of the absorption to visible light photons weakens the detection performance. Zn vacancy has a negative effect on the detection performance. If we want to improve the detection performance of WZ ZnS, Ag-doping will be a good way, but we should reduce the absorption to visible light photons and control the number of vacancy carefully. References B.Y. Geng , X.W. Liu , Q.B. Du , et al . Structure and optical properties of periodically twinned ZnS nanowires . Appl. Phys. Lett . 88 , 163104 ( 2006 ). doi: 10.1063/1.2196827 http://doi.org/10.1063/1.2196827 Structure and optical properties of periodically twinned ZnS nanowires N. Kubota , M. Katagiri , K. Kamijo . Evaluation of Zns-family phosphors for neutron detectors using photon counting method . Nucl. Instrum. Meth. A 529 , 321 - 324 ( 2004 ). doi: 10.1016/j.nima.2004.05.004 http://doi.org/10.1016/j.nima.2004.05.004 Evaluation of Zns-family phosphors for neutron detectors using photon counting method J. Schrier , D.O. Demchenko , A.P. Alivisatos . Optical properties of ZnO/ZnS and ZnO/ZnTe heterostructures for photovoltaic applications . Nano. Lett . 2007 , 7 , 2377 - 2382 ( 2007 ). doi: 10.1021/nl071027k http://doi.org/10.1021/nl071027k Optical properties of ZnO/ZnS and ZnO/ZnTe heterostructures for photovoltaic applications J.H. Li , X.H. Zeng , Z.H. Ji , et al . Electronic structure and optical properties of Ag-doping and Zn vacancy impurities in ZnS . Acta Phys. Sin . 60 , 607 - 613 ( 2011 ). doi: 10.1016/j.pmatsci.2010.10.001 http://doi.org/10.1016/j.pmatsci.2010.10.001 Electronic structure and optical properties of Ag-doping and Zn vacancy impurities in ZnS X. Fang , T. Zhai ,. K. Gautam , et al . ZnS nanostructures: from synthesis to applications . Prog. Mater. Sci . 56 , 175 - 287 ( 2011 ). doi: 10.1016/j.pmatsci.2010.10.001 http://doi.org/10.1016/j.pmatsci.2010.10.001 ZnS nanostructures: from synthesis to applications J. Xie . First-principles study on the magnetism in ZnS-based diluted magnetic semiconductors . J. Magn. Magn. Mater . 322 , L37 - L41 ( 2010 ). doi: 10.1016/j.jmmm.2010.04.031 http://doi.org/10.1016/j.jmmm.2010.04.031 First-principles study on the magnetism in ZnS-based diluted magnetic semiconductors X. Fang , Y. Bando , M. Liao , et al . Single-crystalline Zns nanobelts as ultraviolet-light sensors . Adv. Mater . 21 , 2034 - 2039 ( 2009 ). doi: 10.1002/adma.200802441 http://doi.org/10.1002/adma.200802441 Single-crystalline Zns nanobelts as ultraviolet-light sensors J.H. Yu , J. Joo , H.M. Park , et al . Synthesis of quantum-sized cubic ZnS nanorods by the oriented attachment mechanism . J. Am. Chem. Soc . 127 , 5662 - 5670 ( 2005 ). doi: 10.1021/ja044593f http://doi.org/10.1021/ja044593f Synthesis of quantum-sized cubic ZnS nanorods by the oriented attachment mechanism X.S. Fang , C.H. Ye , L.D. Zhang , et al . Temperature controlled catalytic growth of Zns nanostructures by the evaporation of Zns nanopowders . Adv. Funct. Mater . 15 , 63 - 68 ( 2005 ). doi: 10.1002/adfm.200305008 http://doi.org/10.1002/adfm.200305008 Temperature controlled catalytic growth of Zns nanostructures by the evaporation of Zns nanopowders Z. Wang , L.L. Daemen , Y. Zhao , et al . Morphology-tuned wurtzite-type ZnS nanobelts . Nat. Mater . 15 , 922 - 927 ( 2005 ). doi: 10.1038/nmat1522 http://doi.org/10.1038/nmat1522 Morphology-tuned wurtzite-type ZnS nanobelts Y. Zhao , Y. Zhang , H. Zhu , et al . Low-temperature synthesis of hexagonal (wurtzite) ZnS nanocrystals . J. Am. Chem. Soc . 126 , 6874 - 6875 ( 2004 ). doi: 10.1021/ja048650g http://doi.org/10.1021/ja048650g Low-temperature synthesis of hexagonal (wurtzite) ZnS nanocrystals N. Gao , W. Chen , R. Zhang , et al . First principles investigation on the electronic, magnetic and optical properties of Bi0.8M0.2Fe0.9Co0.1O3 (M= La, Gd, Er, Lu) . Comput. Theor. Chem . 1084 , 36 - 42 ( 2016 ). doi: 10.1016/j.comptc.2016.03.001 http://doi.org/10.1016/j.comptc.2016.03.001 First principles investigation on the electronic, magnetic and optical properties of Bi0.8M0.2Fe0.9Co0.1O3 (M= La, Gd, Er, Lu) W.G. Moulton , C.W. Sherwin . Fast neutron detector . Rev. Sci. Instrum . 33 , 361 - 362 ( 1949 ). doi: 10.2172/4396836 http://doi.org/10.2172/4396836 Fast neutron detector R. Stedman . Scintillator for thermal neutrons using Li6F and ZnS(Ag) . Rev. Sci. Instrum . 31 , 1156 ( 1960 ). doi: 10.1063/1.1716833 http://doi.org/10.1063/1.1716833 Scintillator for thermal neutrons using Li6F and ZnS(Ag) P.G. Koontz , G.R. Keepin , J.E. Ashley . ZnS(Ag) phosphor mixtures for neutron scintillation counting . Rev. Sci. Instrum . 26 , 352 - 356 ( 1955 ). doi: 10.2172/4394603 http://doi.org/10.2172/4394603 ZnS(Ag) phosphor mixtures for neutron scintillation counting J.S. Mccloy , M. Bliss , B. miller , et al . Scintillation and luminescence in transparent colorless single and polycrystalline bulk ceramic ZnS . J. Lumin . 157 , 416 - 423 ( 2015 ). doi: 10.1016/j.jlumin.2014.09.015 http://doi.org/10.1016/j.jlumin.2014.09.015 Scintillation and luminescence in transparent colorless single and polycrystalline bulk ceramic ZnS M. Ardid , J.L. Ferrero , A. Herrero . Study of the background on a ZnS(Ag) alpha counter with a plastic veto detector . Nucl. Instrum. Meth. A 557 , 510 - 515 ( 2006 ). doi: 10.1016/j.nima.2005.10.124 http://doi.org/10.1016/j.nima.2005.10.124 Study of the background on a ZnS(Ag) alpha counter with a plastic veto detector Y. Morishita , S. Yamamoto , K. Izaki , et al . Performance comparison of scintillators for alpha particle detectors . Nucl. Instrum. Meth. A 764 , 383 - 386 ( 2014 ). doi: 10.1016/j.nima.2014.07.046 http://doi.org/10.1016/j.nima.2014.07.046 Performance comparison of scintillators for alpha particle detectors H. Philipsborn . Large-area low-level gross alpha ZnS scintillation counting . Appl. Radiat. Isotopes 67 , 797 - 799 ( 2009 ). doi: 10.1016/j.apradiso.2009.01.020 http://doi.org/10.1016/j.apradiso.2009.01.020 Large-area low-level gross alpha ZnS scintillation counting L. Pujol , J.A. Suarez-Navarro , M. Montero . A method for the selection of the optimum counting conditions in a ZnS(Ag) scintillation detector . Appl. Radiat. Isotopes 52 , 891 - 897 ( 2000 ). doi: 10.1016/s0969-8043(99)00139-6 http://doi.org/10.1016/s0969-8043(99)00139-6 A method for the selection of the optimum counting conditions in a ZnS(Ag) scintillation detector R. Chen , D. Li , B. Liu , et al . Optical and excitonic properties of crystalline ZnS nanowires: toward efficient ultraviolet emission at room temperature . Nano. Lett . 10 , 4956 - 4961 ( 2010 ). doi: 10.1021/nl102987z http://doi.org/10.1021/nl102987z Optical and excitonic properties of crystalline ZnS nanowires: toward efficient ultraviolet emission at room temperature D.A. Reddy , D.H. Kim , S.J. Rhee , et al . Tunable blue-green-emitting wurtzite ZnS: Mg nanosheet-assembled hierarchical spheres for near-UV white LEDs . Nanoscale Res. Lett . 9 , 1 - 8 ( 2014 ). doi: 10.1186/1556-276X-9-20 http://doi.org/10.1186/1556-276X-9-20 Tunable blue-green-emitting wurtzite ZnS: Mg nanosheet-assembled hierarchical spheres for near-UV white LEDs X. Zeng , W. Zhang , J. Cui , et al . Charge transfer and optical properties of wurtzite-type ZnS/(CdS/ZnS)n (n= 2, 4, 8) superlattices . Mater. Res. Bull . 50 , 359 - 364 ( 2014 ). doi: 10.1016/j.materresbull.2013.11.010 http://doi.org/10.1016/j.materresbull.2013.11.010 Charge transfer and optical properties of wurtzite-type ZnS/(CdS/ZnS)n (n= 2, 4, 8) superlattices W. Zhang , X.H. Zeng , H.F. Liu , et al . Synthesis and investigation of blue and green emissions of ZnS ceramics . J. Lumin . 134 , 498 - 503 ( 2013 ). doi: 10.1016/j.jlumin.2012.07.039 http://doi.org/10.1016/j.jlumin.2012.07.039 Synthesis and investigation of blue and green emissions of ZnS ceramics H.C. Ong , R.PH Chang . Optical constants of wurtzite ZnS thin films determined by spectroscopic ellipsometry . Appl. Phys. Lett . 79 , 3612 - 3614 ( 2001 ). doi: 10.1063/1.1419229 http://doi.org/10.1063/1.1419229 Optical constants of wurtzite ZnS thin films determined by spectroscopic ellipsometry X.B. Zhang , H.W. Song , L.X. Yu , et al . Surface states and its influence on luminescence in ZnS nanocrystallite . J. Lumin . 118 , 251 - 256 ( 2006 ). doi: 10.1016/j.jlumin.2005.07.003 http://doi.org/10.1016/j.jlumin.2005.07.003 Surface states and its influence on luminescence in ZnS nanocrystallite C.H. Ye , X.S. Fang , G.H. Li , et al . Origin of the green photoluminescence from zinc sulfide nanobelts . Apll. Phys. Lett . 85 , 3035 - 3037 ( 2004 ). doi: 10.1063/1.1807018 http://doi.org/10.1063/1.1807018 Origin of the green photoluminescence from zinc sulfide nanobelts T. Mitsui , N. Yamamoto , T. Tadokoro , et al . Cathodoluminescence image of defects and luminescence centers in ZnS/GaAs (100) . J. Apll. Phys . 80 , 6972 - 6979 ( 1997 ). doi: 10.1063/1.363770 http://doi.org/10.1063/1.363770 Cathodoluminescence image of defects and luminescence centers in ZnS/GaAs (100) K. Wang , J. Chen , Z. Zeng , et al . Synthesis and photovoltaic effect of vertically aligned ZnO/ZnS core/shell nanowire arrays . Appl. Phys. Lett . 96 ( 12 ): 123105 ( 2010 ). doi: 10.1063/1.3367706 http://doi.org/10.1063/1.3367706 Synthesis and photovoltaic effect of vertically aligned ZnO/ZnS core/shell nanowire arrays M.C. Payne , M.P. Teter , C. Allan , et al . Iterative minimization techniques for ab initio total-energy calculations: molecular dynamics and conjugate gradients . Rev. Mod. Phys . 64 , 1045 - 1097 ( 1992 ). doi: 10.1103/revmodphys.64.1045 http://doi.org/10.1103/revmodphys.64.1045 Iterative minimization techniques for ab initio total-energy calculations: molecular dynamics and conjugate gradients J.P. Perdew , K. Burke , M. Ernzerhof . Generalized gradient approximation made simple . Phys. Rev. Lett . 77 , 3865 - 3868 ( 1996 ). doi: 10.1103/physrevlett.77.3865 http://doi.org/10.1103/physrevlett.77.3865 Generalized gradient approximation made simple E.H. Cui , Y.Z. Zhao , C. Yan , et al . First-principles calculations for electronic, optical and thermodynamic properties of ZnS . Chin. Phys. B 17 , 3867 - 3874 ( 2008 ). doi: 10.1088/1674-1056/17/10/053 http://doi.org/10.1088/1674-1056/17/10/053 First-principles calculations for electronic, optical and thermodynamic properties of ZnS B. Gilbert , B.H. Frazer , H. Zhang , et al . X-ray absorption spectroscopy of the cubic and hexagonal polytypes of zinc sulfide . Phys. Rev. B . 66 , 245205 ( 2002 ). doi: 10.1103/PhysRevB.66.245205 http://doi.org/10.1103/PhysRevB.66.245205 X-ray absorption spectroscopy of the cubic and hexagonal polytypes of zinc sulfide A. Goldmann , W. Gudat , O. Rader . Electronic structure of solids: Photoemission spectra and related data . New York : Springer , 1994 . Electronic structure of solids: Photoemission spectra and related data J.P. Perdew , S. Kurth , A. Zupan , et al . Accurate density functional with correct formal properties: A step beyond the generalized gradient approximation . Phys. Rev. Lett . 82 , 2544 ( 1999 ). doi: 10.1103/PhysRevLett.82.2544 http://doi.org/10.1103/PhysRevLett.82.2544 Accurate density functional with correct formal properties: A step beyond the generalized gradient approximation G. Onida , L. Reining , A. Rubio . Electronic excitations: density-functional versus many-body Green’s-function approaches . Rev. Mod. Phys . 74 , 601 ( 2002 ). doi: 10.1103/RevModPhys.74.601 http://doi.org/10.1103/RevModPhys.74.601 Electronic excitations: density-functional versus many-body Green’s-function approaches R.O. Jones . Density functional theory: Its origins, rise to prominence, and future . Rev. Mod. Phys . 87 , 897 ( 2015 ). doi: 10.1103/RevModPhys.87.897 http://doi.org/10.1103/RevModPhys.87.897 Density functional theory: Its origins, rise to prominence, and future Q. Li , C. Wang . Fabrication of wurtzite ZnS nanobelts via simple thermal evaporation . Appl. Phys. Lett . 83 , 359 - 361 ( 2003 ). doi: 10.1063/1.1591999 http://doi.org/10.1063/1.1591999 Fabrication of wurtzite ZnS nanobelts via simple thermal evaporation O. Zakharov , A. Rubio , X. Blase , et al . Quasiparticle band structures of six II-VI compounds: ZnS, ZnSe, ZnTe, CdS, CdSe, and CdTe . Phys. Rev. B 50 , 10780 - 10787 ( 1994 ). doi: 10.1103/physrevb.50.10780 http://doi.org/10.1103/physrevb.50.10780 Quasiparticle band structures of six II-VI compounds: ZnS, ZnSe, ZnTe, CdS, CdSe, and CdTe 10.1007/s41365-017-0194-y This work was supported by the National Natural Science Foundation of China (Nos. 11275071 and 11305061), the Fundamental Research Funds for the Central Universities (Nos. 2014MS53 and 2014ZZD09), and the Student’s Platform for Innovation and Entrepreneurship Training Program of North China Electric Power University (No. 15129). 2016-06-12 2016-08-30 2016-09-08 2017-01-31 2017-03-01 2021-04-11 © China Science Publishing & Media Ltd. (Science Press), Shanghai Institute of Applied Physics, the Chinese Academy of Sciences, ChineseNuclear Society and Springer Nature Singapore Pte Ltd. 2017 This is a post-peer-review, pre-copyedit version of an article published in Nuclear Science and Techniques. The final authenticated version is available online at: http://dx.doi.org/10.1007/s41365-017-0194-y http://dx.doi.org/10.1007/s41365-017-0194-y . 2017 Nuclear Science and Techniques 03 28