Poster Speaker: Xiao-Ping Zheng

Dependence of thin film growth on substrate temperatureKinetic Monte Carlo simulation of thin film growth

Xiao-Ping Zheng 1 ) 2) Pei-Feng Zhang2) Duo-Wang Fan1)1: Key Laboratory of Opto-Electronic Technology and Intelligent Control, Ministry of Education, Lanzhou Jiaotong

University, Lanzhou 730070, China, 1: keylab@lzjtu.mail.cn)2: Institute of Electronic Information Science and Technology, Lanzhou city University, Lanzhou 730070, China,:

zxp@lztc.edu.cn and zpf@sina.com

Abstract A three-dimensional KMC technique has been developed for simulating growth of thin films. The surfaceroughness and the relative density of the films were simulated as functions of growth substrate temperature anddeposition rate.

IntroductionThe film growth mechanism is still less than well understood on a microscopic level[1-3]. In this paper, a three-dimensional kinetic Monte Carlo (KMC) technique has been developed for simulating growth of thin films in basis ofbond-counting KMC. The model involves incident atoms attachment, surface diffusion of the atoms on the growingsurface, and detachment of atoms from the growing surface. A great improvement was made on calculation of theactivation energy for the surface atom diffusion. The all processes were realized by Monte Carlo simulation withoutany assumption.

Model and MethodThis work was based on our previous work[4].The attachment rate of atoms was given by the number of incidentatoms per unit time. The diffusion rate of a single adatom was defined as the probability of a diffusion jump per unittime and given by the Arrhenius-type expression

V = VO exp (- AE/kBT) (1)

where vO is the frequency of atom vibrations and assigned a value of v0= (2kBT)/h, AE is the activation energy. Theactivation energy AE is determined by taking the difference between Emax and Eini., where Emax is the maximumactivation barrier Emax between two lattice sites, Eini. is the potential in the initial site.

Results and discussionThe dependence of the growing surface roughness on the substrate temperature at various deposition rates is shownin Fig. 1. The average thickness of the film is 8 layers. It can be seen that, for every deposition rate, there exists anoptimum growth temperature at which the surface roughness is minimum.The relative density vs. the substrate temperature under various deposition rates is shown in Fig.2. The averagethickness is 80 layers. It can be seen that, with increasing the substrate temperature, the relative density increasesand approaches to 1 at a certain temperature for every deposition rate. The relative density is easier to saturate forlower deposition rates.Figure 3 shows a snapshot of growing film at temperature of 200 K and deposition rate of 3.2 lay./s. The averagethickness of the film is 20 layers.

2.5 \ l/ 1.02Deposition rate /lay)s

*0.032* 0.320 1.00A3.200

C/) r 1 0921 *X3X32000200 0 320000 0 0098

U) roughness on Deposition rate tIay.s0) 032~~~~~~~~~~~~~~~~~~9

+320.0000_____________________________________0.90 I I I I I

200 30 40 50 60 70 80200 250 300 350 400 450 500 550 600 650 700

Substrate temperature 1K Substrate temperature /K

Fig. I The dependence of the growing surface. Fig. 2 The relative density vs. the substrateroughness on substrate temperature. temperatures.

1-4244-1591-8/07/$25.00 C2007 IEEE

Poster Session 4. Pi 19

310

Poster Speaker: Xiao-Ping Zheng

Fig. 3 The snapshot of growing film at T=200K with a deposition rate of3.2 lay./s. The average thickness of film is 20 layers

ConclusionThe results showed that there exists a optimum growth temperature at certain deposition rate, the surface roughnessdecrease and the relative density increase with the increasing substrate temperature, the surface roughness isminimum and the relative density of film saturates when the substrate temperature approach respective optimumgrowth temperature, then the surface roughness increases with the increasing substrate temperature.

AcknowledgementProject supported by the National Natural Science Foundation of China (Grant No.10574059), the Natural ScienceFoundation of Gansu Province, China (Grant No. 3ZS042-B25-033), 'Qing Lan' Talent Engineering Funds ofLanzhou Jiaotong University,

Reference1 Graeme Henkelman et al, Phys.Rew.Lett.,90(2003), 1012 M.G.Lagally et al, Nature (London), 417(2002), 9073 Wang L G et al, P,Surf. Sci., 473 (2001), 254 Zhang P F et al, J. Korean Phys. Soc., 46(2005), 92

Xiaoping, Zheng (Authorl) received her BS degree from Lanzhou University of China, and herMS and PhD degrees from Lanzhou University of Cina in 1990, 1994 and 2002, respectively, allin Physics. Her research interest has been in the areas of computational materials science andmagnetic functional materials. She has authored 35 papers in leading technical journals andconferences.

311

Poster Session 4. Pi 19