Microstructures

The magnetron sputtered titanium thin film coatings microstructures prepared over different substrates are discussed in this section. The deposition parameters play an important role in determining the final microstructural property of deposited thin films. The crack observed in thin film coating is because of the sample preparation in which the samples are bent to analyze morphological properties of thin films deposited. The significant changes observed during these titanium depositions are noted for interpretations alongside respective micrographs supporting the case. The titanium coatings deposited over copper substrates is taken into consideration for better understanding. The deposition of titanium coatings is done for 10 minutes with increasing the power from 1 to 2 A respectively. From Figures 33 and 34, the respective micrographs represent columnar microstructures which are dense in nature and there is no porosity present in the surface. The sample S012 micrographs is represented in Figure 33 followed by Figure 34 which represents FESEM images of sample S015.

Figure 33. FESEM images of microstructure of sputtered Ti coatings on copper (S012), the coatings exhibited dense, uniform columnar microstructure with coarser surface morphology. The deposition parameters used for this sputtering are as follows current – 1 A, deposition time -10 minutes, sputtering pressure - 5 mtorr.

Figure 34. FESEM images of microstructure of sputtered Ti coatings on copper (S015), the coatings exhibited dense, uniform columnar microstructure only slightly exhibiting coarse surface morphology. The deposition parameters used for this sputtering are as follows current – 2 A, deposition time - 10 minutes, sputtering pressure – 5 mtorr.

The deposition time of five minutes is considered and the corresponding changes observed in thin film coatings are analyzed in this section. The fused columnar microstructure is predominant in these samples namely S018 and S019. The power value is increased from 1 to 2 A with constant 1 A as increment value. The microstructures of these thin film coatings are well-bonded structures which are uniform, dense in nature with no porosity present in it. The Figures 35 and 36 presented below represents the copper samples S018 and S019 correspondingly, and the current used for this titanium deposition is 1 and 2 A respectively.

Figure 35. FESEM images of microstructure of sputtered Ti coatings on copper (S018), the coatings exhibited dense, well bonded, non-porous, uniform columnar microstructure with coarser surface morphology. The deposition parameters used for this sputtering are as follows current – 1 A, deposition time – 5 minutes, sputtering pressure – 5 mtorr.

Figure 36. FESEM images of microstructure of sputtered Ti coatings on copper (S019), the coatings exhibited well bonded, nonporous, dense, uniform columnar microstructure with coarser surface morphology. The deposition parameters used for this sputtering are as follows current – 2 A, deposition time - 5 minutes, sputtering pressure – 5 mtorr.

The microstructure changes for the following samples S043 and S044 is analyzed in this section. The titanium thin film coating is deposited over copper substrates with high sputtering pressure is evaluated. The sputtering pressure used for these above mentioned samples are 10 and 20 mtorr respectively. The other important deposition parameters used for this deposition are as follows, deposition time - 10 minutes, current – 2 A. The morphological changes observed in S043 is the columnar grains which are dense in nature, grains are non-uniform, however the surface of the grains are coarser in nature with needle like grains thus representing coarser surface. Figures 37 and 38 represents the cross-sectional micrographs of titanium thin film deposition for samples S043 and S044 respectively. The micrograph from Figure 38 clearly represents the columnar microstructure, which is needle-shaped, flake-like, coarse, thick grains in nature. The columnar growth is non-uniform and the direction of grain growth is random in nature.

Figure 37. FESEM images of microstructure of sputtered Ti coatings on copper (S043), the coatings exhibited dense, non-uniform columnar microstructure with coarser surface. The deposition parameters used for this sputtering are as follows current - 2 A, deposition time - 10 minutes, sputtering pressure - 10 mtorr.

Figure 38. FESEM images of microstructure of sputtered Ti coatings on copper (S044), the coatings exhibited dense, non-uniform, needle like columnar microstructure, grains are randomly oriented with coarser surface morphology. The deposition parameters used for this sputtering are as follows current – 2 A, deposition time - 10 minutes, sputtering pressure – 20 mtorr.

The microstructure of sample S042 is of major importance as the deposition time of 30 minutes is used. The growth of the columnar grains is slightly inclined towards an angle. The other interesting properties of columnar microstructure in this film growth are well-bonded dense microstructure, coarser grain surface and uniform in nature. Figure 39 represents the microstructure of titanium thin film sample S042.

Figure 39. FESEM images of microstructure of sputtered Ti coatings on copper (S042), the coatings exhibited dense, uniform columnar microstructure, slightly inclined columnar grains is observed with coarser surface morphology. The deposition parameters used for this sputtering are as follows current – 2 A, deposition time - 30 minutes, sputtering pressure - 5 mtorr.

The samples S030 and S031 are taken into consideration in this section. These samples use stainless steel as substrate materials and the current is increased from 1 A to 2 A for the sample S030 and S031 respectively. The sample S030 and S031 represents similar thin columnar structures which are dense, fused and uniform in nature. Figure 40 represents the micrographs of S031.

Figure 40. FESEM images of microstructure of sputtered Ti coatings on stainless steel (S031), the coatings exhibited dense, uniform columnar microstructure with relatively smooth surface morphology. The deposition parameters used for this sputtering are as follows current – 2 A, deposition time - 3 minutes, sputtering pressure – 5 mtorr.

The next set of samples which are considered for investigation are S048 and S049. The resultant microstructures of both the samples are similar in nature which is well bonded dense columnar microstructure. Figure 41 represents the FESEM micrographs of sample S048.

Figure 41. FESEM images of microstructure of sputtered Ti coatings on stainless steel (S048), the coatings exhibited dense, well-bonded, thick, uniform columnar microstructure with slightly smoother surface morphology. The deposition parameters used for this sputtering are as follows current – 2 A, deposition time – 10 minutes, sputtering pressure – 5 mtorr.

The sample S055 is etched with argon plasma and titanium thin film deposited using sputtering process is analyzed using FESEM. The crystal morphology of S055 is fully dense well bonded columnar microstructure as shown in Figure 42.

Figure 42. FESEM images of microstructure of sputtered Ti coatings on stainless steel (S012), the coatings exhibited dense, uniform columnar microstructure with smooth surface morphology. The deposition parameters used for this sputtering are as follows current – 2 A, deposition time - 3 minutes, sputtering pressure – 5 mtorr.

The stainless steel substrate is heated for 30 minutes for S039 and titanium thin film is deposited. From FESEM images, it is clear that the well bonded columnar grains are dense and it is uniform. Figure 43 represents the sample S039 with titanium deposition prior to the deposition substrate heating is accomplished. The sputtering experiments data for thin film titanium coatings is summarized in Table 9.

Figure 43. FESEM images of microstructure of sputtered Ti coatings on stainless steel (S039), the coatings exhibited dense, well bonded, uniform columnar microstructure with smooth surface morphology. The deposition parameters used for this sputtering are as follows current – 2 A, deposition time - 10 minutes, sputtering pressure – 5 mtorr.

Table 9. Summarizes the data of sputtering sample used for Titanium sputtering deposition and its respective deposition parameters, resultant thickness value and its corresponding deposition rate value used in section 5.1. The symbols which are used in Table 9 are given as follows current (I), voltage (U) and deposition rate (Dep. rate).