Properties of C and CN Films Prepared by Mass-Separated Hyper-Thermal Carbon and Nitrogen Ions
- PDF / 372,936 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 65 Downloads / 193 Views
ABSTRACT Amorphous carbon films and CN films were prepared by ion beam deposition using isotopically mass-separated, hyper-thermal (50-400eV) ion species such as 12C-, 12C 14N or simultaneous 12C2- and 1nN' under high vacuum condition. Film properties such as structures, bonding states, compositions, etc. were investigated. The optical band gaps of amorphous carbon films deposited by using 12C 2 - ions or CN films deposited by using I2C4N- ions were estimated from optical constants. The gaps were about 2.3eV for the amorphous carbon films and about 0.8 eV for the CN films. Energy dependence of optical constants of CN films formed by simultaneous deposition of C2- and N' was investigated. The refractive index (n) and extinction coefficient (k) at k = 675nm increased 1.5 to 2.4 and 0.3 to 1.3, respectively, with increasing N' kinetic energy. The relations between bonding states and kinetic energy of hyper-thermal ions are discussed.
INTRODUCTION Amorphous carbon (a-C) has attracted a lot of researchers for a long time because it has interesting properties such as high hardness, chemical inertness, high electric resistivity, etc. Nowadays it is used to produce a protective coating material for hard discs. There are a lot of ways to produce a-C films like filtered cathodic vacuum arc [1], laser ablation of graphite [2,3], etc. Among these methods, an ion beam deposition (IBD) method is an interesting way to produce a-C films. The films are deposited by irradiation of direct hyper-thermal (several tens to hundreds eV) carbon ions on a substrate. Using the IBD method, the sp3/sp 2 bonding ratio of a-C is able to be varied up to the maximum value, 0.8 in accordance with kinetic energies of carbon ions [4,5]. J. L. Robertson et al. [6] reported that a diamond epitaxial film was also formed by the IBD method. As interest of a hard material, undiscovered metastable crystalline P-C3 N 4 has been predicted by Liu and Cohen in 1989 [7]. It is expected to have hardness comparable to or more than that of diamond. However there is no clear evidence of its existence in spite of much efforts of producing it by means of various ways such as arc discharge deposition [8], chemical vapor deposition [9], sputter deposition [10], ion beam deposition [11,12,13], reactive pulsed laser ablation [14], etc. Another group discusses the stability of other polytypes of crystalline C 3 N 4 like an cc phase, a cubic phase, etc [15]. From the above discussions, it is difficult to say that C-N system is clearly understood. In this study, properties such as composition, impurity, structure, bonding states of C and CN films deposited by hyper-thermal 12C2- and 12C14 N were compared to each other. Furthermore, correlation between ion's kinetic energy and ratios of bonding states in CN films by simultaneous deposition of C2- and N' was investigated.
307 Mat. Res. Soc. Symp. Proc. Vol. 504 01998 Materials Research Society
EXPERIMENT Isotopically mass-separated positive and negative ions, 1C 2- (200eV), 12C 4N(200eV) and C2- (200eV) + N+ (50-400eV) whi
Data Loading...
