## 3 Results and Discussion
Since no oxide associated peaks were found on the as-sputtered sample, the oxidation of Mo thin films may occur during annealing due to furnace leakage, or after annealing because the sample is still at a fairly high temperature when unloaded from the furnace and cooled down in an ambient environment. Figure 4: X-ray diffraction (XRD) patterns of Mo thin films, as a function of annealing temperature. Mo Bragg peaks originating from (110), (200), and (211) planes are labelled with dotted lines for guides to the eye. Other unlabeled peaks are associated with Mo oxides phases. Figure 3: Surface roughness of Mo thin films, as a function of annealing temperature. Linear fit of measurement data from 700 \({}^{\circ}\)C to 1100 \({}^{\circ}\)C is also demonstrated. To investigate the degree of Mo crystalline orientation along a certain plane (_hkl_), the texture coefficient \(C_{hkl}\) is determined through Equation (1) [9; 15]:  
\[C_{hkl}=\frac{\frac{I_{hkl}}{I_{0 kl}}}{\frac{1}{n}\sum_{n}\frac{I_{hkl}}{I_{0 kl}}} \tag{1}\]  
where \(n\) is the number of reflections (i.e., identified Bragg peaks); \(I_{hkl}\) and \(I_{0 kl}\) are the measured intensity of the (_hkl_) reflection from the thin film sample, and the intensity of the (_hkl_) reflection from the corresponding powder sample, respectively, as explained in Reference [15]. A completely randomized sample will have unity \(C_{hkl}\) values on all planes, whilst values for samples with preferred growth direction will deviate from 1 [15]. To study the preferred orientation of each Mo thin film, the standard deviation \(\sigma\) of all \(C_{hkl}\) values compared to randomly orientated samples is determined by Equation (2) [9; 15], in which smaller values of \(\sigma\) correspond to a lesser preferential degree of alignment of the sample. \(C_{hkl}\) and \(\sigma\) for each Mo thin film are summarized in Table 1.  
\[\sigma=\sqrt{\sum\frac{1}{n}(C_{hkl}-1)^{2}} \tag{2}\]  
As-sputtered Mo and those films annealed below 900 \({}^{\circ}\)C (included) demonstrated strong orientation preference in the (110) direction, since \(C_{110}\) of these samples were at least two times larger than the value for other orientations. On the other hand, the texture coefficient for the (200) plane was the smallest, and the change was marginal for all samples. Moreover, the texture coefficient for the (211) plane first decreased from As-Mo to Mo-800, and then recovered to the level of As-Mo when annealed at 900 \({}^{\circ}\)C. Finally, \(C_{211}\) increased to near 1.5 when the samples were annealed at 1000 \({}^{\circ}\)C and 1100 \({}^{\circ}\)C, respectively. These changes indicated that (110) is the dominant crystalline orientation on as-sputtered Mo thin film, and for samples annealed at 700-900 \({}^{\circ}\)C. However, this preference was lost and shifted to the (211) plane when the annealing temperature was above 900 \({}^{\circ}\)C. From Table 1, the drop in \(C_{110}\) overwhelms the increase in \(C_{211}\). Therefore the \(\sigma\) value follows the trend of the \(C_{110}\)- and a peak value of 0.73 was obtained on sample Mo-800. Such changes in texture coefficient and preferred orientation were results of the Mo recrystallization process, as pointed out previously. Crystallite size of Mo (\(D_{Mo}\)) were estimated using the Scherrer Equation from (110) XRD peaks [16]:  
\[D_{Mo}=\frac{0.9\lambda}{\beta_{110}cos\theta_{110}} \tag{3}\]  
where \(\lambda\) is the X-ray wavelength of Cu K\(\alpha\) (0.154 nm), \(\beta\) is the full width at half maximum (FWHM) of the diffraction peak at a Bragg angle of \(2\theta\) for the (110) plane. The calculated Mo crystallite sizes from XRD patterns are listed and plotted in Table 1 and Figure 5 (line + solid sphere), respectively. From Table 1, the as-sputtered Mo has an estimated crystallite size of 18.5 nm. Upon annealing,