Ag Doped Amorphous Carbon Films: Structure, Mechanical and Electrical Behaviors

doi:10.15541/jim20180263

Abstract

Abstract:

By adjusting sputter current from 1.3 A to 2.0 A in reactive magnetron sputtering deposition processes, Ag doped amorphous carbon films (a-C:Ag) with doping content from 0.7at% to 41.4at% were prepared. The influence of Ag content on structure, component, mechanical and electrical properties of a-C:Ag films were systematically studied. The results showed that Ag atoms were dissolved in amorphous carbon matrix at low Ag content (0.7at% to 1.2at%) conditions. However, Ag nanocrystal with a size around 6 nm formed when Ag content increased to 13.0at%. With the increase of Ag content, the size of sp ² clusters in the amorphous carbon matrix increased while the structural disorder degree decreased. Stress test indicated that in the low Ag content range, Ag atoms were dissolved in carbon matrix which played a pivotal role in promoting relaxation of bond length and angle distortion, thereby the film stress was reduced. Ag atoms started to form Ag nanocrystals as the Ag content increased. As a result, film stress would be reduced due to release of excessive distortion by sliding and diffusion at the grain boundaries. When Ag content reached 37.8at%, a-C:Ag exhibited transition from metal to semiconductor characteristic near 11.6 K. However, as the Ag content increased to 41.4at%, the films displayed semiconducting characteristics in the whole test temperature range (2-400 K) and exhibited typical thermal activation mechanism within temperature range of 164-400 K.

Key words: amorphous carbon, Ag doping, structure characterization, mechanical property, electrical behavior

CLC Number:

TQ127

Ren-De CHEN, Peng GUO, Xiao ZUO, Shi-Peng XU, Pei-Ling KE, Ai-Ying WANG. Ag Doped Amorphous Carbon Films: Structure, Mechanical and Electrical Behaviors[J]. Journal of Inorganic Materials, 2019, 34(4): 387-393.

Figures/Tables 11

Table 1 Ag concentration, O concentration, film thickness and average deposition rate varied with sputtering current and power

Sputtering current /A	Sputtering power /W	Ag concentration /at%	O concentration /at%	Thickness /nm	Deposition rate /(nm?min^-1)
1.3	582	0.7	30.2	364.5	18.2
1.4	602	0.8	26.5	358.3	17.9
1.5	647	1.2	27.2	508.5	25.4
1.6	859	13.0	45.2	725.4	36.3
1.8	788	37.8	32.9	1409.1	70.5
2.0	856	41.4	32.2	1720.4	86.0

Fig. 1 Typical XPS spectra for the a-C:Ag films (a), and representative Ag 3d spectra of the films with 41.4at% Ag (b)

Fig. 2 XRD patterns of a-C:Ag films with various Ag concentrations

Fig. 3 (a) Sample for TEM prepared by FIB, (b) HRTEM and SAED of sample with 1.2at% a-C:Ag

Fig. 4 Typical Raman spectra a-C:Ag films with different Ag concentrations (a) and the fitting result of a-C:Ag film with 0.7at% Ag atoms (b)

Table 2 The fitted G-peak position, ID/IG and FWHM of G-peak varied with different Ag concentrations

Ag concentration /at%	G-peak position/cm^-1	I_D/I_G	FWHM of G-peak/cm^-1
0.7	1533.0	0.75	159.4
0.8	1535.9	0.79	151.6
1.2	1539.8	0.85	151.4
13.0	1582.5	1.94	122.5
37.8	1566.4	2.15	123.6
41.4	1580.7	2.68	110.0

Fig. 5 Surface topographies of a-C:Ag films with different Ag concentrations (a) 0.7at%; (b) 0.8at%; (c) 1.2at%; (d) 13.0at%; (e) 37.8at%; (f) 41.4at%

Fig. 6 Hardness (a) and elastic modulus (b) as a function of Ag concentration

Fig.7 Residual compressive stress of a-C:Ag films as a function of Ag concentration

Fig. 8 Temperature dependence of resistivity in a-C:Ag film with 37.8at% Ag in the range of 8~400 K (a) and the a-C:Ag with 41.4at% Ag in the range of 2~400 K (b)

Fig. 9 Plot of lnρ vs reciprocal temperature in the range of 164-400 K for a-C:Ag film with 41.4at% Ag

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