| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2016) | |
| Nanomaterials | Tuesday Sessions |
| Session NM-TuP |
| Session: | Nanomaterials Poster Session |
| Presenter: | Moon-Deock Kim, Chungnam National University, Republic of Korea |
| Authors: | M.-D. Kim, Chungnam National University, Republic of Korea B.-G. Park, Chungnam National University, Republic of Korea J.-W. Hwang, Chungnam National University, Republic of Korea W.-C. Yang, Dongguk university, Republic of Korea D.-Y. Kim, Dongguk university, Republic of Korea K.-B. Chung, Dongguk university, Republic of Korea |
| Correspondent: | Click to Email |
In this work, we have investigated the kinetic process and adatoms mechanism of four different top shapes of catalyst-free Ga(In)N nanorods (NRs) namely flat, taper, hammer, and mushroom structures were grown in holes of a patterned Si (111) substrate by plasma-assisted molecular beam epitaxy. Arrays of nano-holes with diameter of 80 nm on the Si substrate were obtained by using of self-assembled silica nanospheres as a nano-hole mask. The silica nanospheres coated on the Si substrate and then spread using a spin-coating method. A 10 nm-Ti deposited after dry etching to sizes control and then removed silica nanospheres by chemical etching. Different top shapes of Ga(In)N were obtained by varying the growth conditions namely growth temperature and N2 plasma power, and the morphology evolution was explained based on the interrelation between sidewall diffusion and direct impingement during the NRs growth. GaN NRs grown at the growth temperature (Tg) and Ga flux of 650 °C and 5x10-7 Torr, respectively, were used as the buffer for the subsequent growth of GaN NRs with different top shapes. GaN NRs with flat top (Fig. 1(a)) was obtained without altering the growth conditions that was used for the buffer growth. When the Tg was increased gradually from 590 °C to 650 °C under Ga flux of 1x10-7 Torr, we obtained GaN NRs with top tapered shape (Fig. 1(b)). On the other hand, hammer shaped GaN NRs (Fig. 1(c)) were obtained when the Tg was reduced gradually to 570 °C, while keeping the Ga flux 1x10-7 Torr during the growth of GaN NRs. Furthermore, mushroom shaped Ga(In)N nanostructure (Fig. 1(d)) on top of GaN NRs were obtained when introducing In flux of 1x10-7 Torr at Tg ~ 350 °C under the same Ga flux. The variations in the shape of GaN NRs are explained by the interrelation of sidewall diffusion and the supersaturation of adatoms at the top surface [1, 2]. Photoluminescence measurements revealed higher light emission for tapered GaN when compared to non-tapered structure. APSYS simulations were further conducted to theoretically confirm the observed experimental results. We believe that our results can provide crucial information for the shape controlled growth of GaN NRs with diverse nanostructures and promising approach for the realization of high brightness LEDs.
Fig. 1 SEM images of GaN NRs with different top shape (a) flat, (b) tapered, (c) hammer and of GaInN with (d) mushroom
REFERENCES
[1] Xin Yin, Jian Shi, Xiaobin Niu, Hanchen Huang, and Xudong Wang, Nano let., 15, 7766 (2015)
[2] T. Stoica, R. Meijers, R. Calarco, T. Richter, and H. Luth, J. Cryst. Growth 290, 241 (2006)