In order to avoid the possibility of over-nitridation, a lower ammonia flow of 0.25 and 0.125 mol/min was set for samples E and F, respectively, and other

growth parameters were as the same as those set for sample C. Figure 1 The pulse timing’s schematic diagrams of samples A to D. Characterization The thickness of film was measured by in situ growth monitoring curves (Panalytical X’pert PRO X, Panalytical, Almelo, The Netherlands). The surface morphology and smoothness of the as-grown samples were characterized by atomic force microscopy (AFM, PicoSPM and PSI XE-100, Molecular Imaging, Ann Arbor, MI, USA) and scanning electron microscopy (SEM, LEO 1530, LEO Elektronenmikroskopie GmbH, Oberkochen, Germany) equipped with an energy-dispersive X-ray spectrometer (EDX). The structural quality and the In composition of InN films were evaluated by X-ray diffraction (XRD) in a X’ Pert GSK2118436 research buy PRO system. Results and discussion In the ideal indium bilayer construction process, we need to deposit one indium monolayer in each pulse, thus this new indium monolayer would construct an indium bilayer with the top indium monolayer which we had deposited in last pulse [17]. Figure 2 shows the in situ growth monitoring interferometer curves of samples A to D. One can observe that in the InN growth

stage, the vibration of all four sample’s curves have experienced nearly equal phase shift. According to this phase shift, we can learn more easily calculate the average InN film’s thickness of them, which is about 170 nm. Also this result Fulvestrant has been confirmed by practical measurement in the SEM cross-sectional observation (see SEM cross-sectional photos in Figure 3). Thus, the InN deposition thicknesses per period of samples A, B, C, and D are about 9.5, 4.7, 2.4, and 1.8 Å, respectively.

According to the (0001) lattice constant c of wurtzite InN, the thickness of one In-N monolayer (c/2) is about 2.8 Å. Comparing to this value, sample C’s growth thickness of each pulse is the closest one. Figure 2 The in situ growth monitor interferometery curves of samples A to D. Figure 3 SEM images of samples A to D. (A1, B1, C1 D1) The top view and (A2, B2, C2, D2) the side view images of samples A to D, respectively. Figure 3 5-FU shows the SEM images of surface morphology and cross sections of samples A to D. From the top view of sample A (A1), one can see some obvious dark holes on the surface, indicating the formation of vacancies due to In accumulation in droplets. The formation of holes and droplets easily leads to a pretty rough surface (rms = 33, from AFM scanning result), as shown in Figure 3A2. As we know, the melting temperature of metal In is only about 157°C. Thus, under the growth temperature of InN (550°C), the pulsed deposition of In for a long duration time may form a thick liquid In layer on the surface. By the effect of surface tension, In droplets in large size would come into being quickly.