【正文】 C, which is indicative of the improvement of MRO. Recently, the calculation of R. L. C. Vink et al. [19] using 1000atom configurations shows that to some degree, ITA/ITO depends on Δθ which is related to SRO, and there is an approximately linear relation between ITA/ITO and Δθ . But this linear relationship is not apparent in our experiment as shown in Fig. 5. The hydrogen in aSi:H thin film is a key factor for determining the properties of materials. Compared to the silicon in work that has a rigid nonequilibrium structure, the hydrogen has different bonding properties due to a more mobile equilibrium structure. The information on the different types of hydrogen bonding can be extracted from the infrared spectroscopy. The phonon modes of Si\H bonds in aSi:H occur in three energy bands [20]: (i) a wagging mode at 630 cm?1 which is always present, (ii) a doublet in 800– 900 cm?1 whose shape and intensity depend on deposition conditions, and (iii) modes in range 2020– 2100 cm?1. Fig. 6 shows a set of IR transmittance spectra for samples prepared at different gas temperatures. Let us now consider the band at 630cm?1 first. It is observed that its intensity decreases slightly with the increase of Tg. The study of Shanks et al. [10] reveals that the integrated intensity of this band is the best measure of hydrogen concentration but the other lines are less reliable. Consequently, the hydrogen content CH in aSi:H thin films can be calculated via where β is the absorption coefficient, and N= 1022/cm?3 is the atomic density of crystalli。 C, rms= nm, d= nm. The thickness d is obtained from the SE measurement. As shown in Table 1, there is a decrease in the value of Δθ from to with the increase of Tg. Stolk et al. [18] show that by measuring carrier life time, it is possible to relate the concentration Ns of defects in aSi:H to the change of Δθ . As shown in Fig. 5, there is an evident positive correlation between Δθ and Ns. We speculate here that when larger bond angle deviation occurs, the formation of defects is necessary for enhancing the stability and lowering the strain energy of amorphous work. As mentioned above, the more defects amorphous work generates in thin films, the larger both ILA/ITO and ILO/ITO from Raman measurement are. However, what is interesting here is that the variation of ILA/ITO is opposite to that of ILO/ITO in our experiment. As shown in Table 1, with the increase of Tg from RT to 160 176。 C,rms= nm, d= nm。 C, rms= nm, d= nm。 the inset is a typical Raman spectrum of aSi:H and its Gaussdeconvolution. Fig. 2. Threedimensional AFM images of aSi:H thin films deposited at different Tg. (a) RT, rms= nm, d= nm。 C, and 160 176。C. It shows that the increase of Tg can reduce the dangling bonds in aSi:H thin films to a large extent. Raman scattering has been extensively used to estimate the evolution of work structure due to its intensity sensitive to the structural disorder in solids. As shown in the inset of , the Raman spectrum of aSi:H thin film consists of several vibrational modes. The band at about 150 cm?1, associated with transverseacoustic (TA) vibrational modes, is proportional to the density of dihedral angle fluctuations, reflecting the mediumrange order (MRO) of amorphous work [12]. The TO phonon band at about ω TO=480 cm?1 is sensitive to the rootmean square bondangle variation Δθ [13]. A shift of TO band position toward higher frequencies and a decrease in the peak width (Γ TO) are consistent with the increase in the shortrange order (SRO). Moreover, several putational studies show that the relation between Γ TO and the SRO can be quantified. On the basis on the continuous random work model, Beeman et al. have obtained a linear relation Γ TO=15+6Δθ , which is often used by experimentalists to determine Δθ from Raman measurements [14]. The presence of the longitudinal acoustic band (LA) at 300 cm?1 and the presence of the longitudinal optical band (LO) at 410 cm?1 are related to the coordination defects in thin films, and the more defects the larger values of ILA/ITO and ILO/ITO ratio [15], where I stands for the integral intensity of the corresponding vibrational mode. The peaks at about ω 2LA=610 cm?1 and ω 2TO=960 cm?1 are overtones of the main aSi ω LA and the main aSi ω TO, respectively [16]. In our case, the Raman data between 600 cm?1 and 1000 cm?1 are not analyzed due to the overlap of overtones. The Raman spectra of aSi:H thin films depositedat different gas temperatures are shown in Fig. 4. It can be seen that all the thin films studied here have typical Raman features of aSi, namely, the broad TO peak at approximately 480 cm?1. The TO peak position shifts by cm?1 with the increase of Tg but is still in the amorphous region. On the other hand, Γ TO decreases by cm?1. This result indicates that the increase of gas temperature leads to the improvement of SRO in aSi:H thin films but not to the crystallization. In addition, it is reported that the shift of ω TO also depends on the intrinsic stress in the thin films [17]. According to the changes in Γ TO, the Δθ has been estimated to describe quantitatively the variation of SRO. Fig. 3. Derivative ESR spectra of aSi:H thin films deposited at different Tg, the data in the inset correspond from top to bottom to Tg=RT, 80 176。 C to 160 176。 C and 160 176。 C. Fig. 1. Schematic configuration of the PECVD system. 3. Results and discussion . Structural properties of aSi:H thin films Through AFM observations the information about the morphological properties of aSi:H thin films can be extracted. In our case, the scan is performed on a 1 μ m 1 μ m area with the tapping mode. In Fig. 2, we present the threedimensional AFM images of the samples deposited at Tg of room temperature (RT), 80 176。 C. . Charac