Equilibrium shape of nano-cavities in H implanted ZnO

Abstract

showed a similar peak centered at 650 nm. This indicates that the PL and EL processes could be related to the same origin. Even though the center of EL peak was around 650 nm, overall EL peak showed the broad spectrum in the range of 500-850 nm. EL intensity was increased with increasing the forward voltage, as shown in Fig. 4(a). Figure 4(b) shows the light output power of Si NC LED with a SiC film as a function of the forward voltage. Light output power of the Si NC LED was measured from the topside of the Si NC LED, not from integrated measurement because it is very difficult for the total light output power from the Si NC LED to measure or calculate without a package process. With increasing the forward voltage, the light output power was linearly increased, indicating that the light emission was increased as more electrons and holes were injected into the Si NCs into a SiC film. The WPE, which means the power efficiency (output power/input power), is very important in LED applications. Based on the I-V data and light output power, the WPE of Si NC LED with a SiC film at 20 mA ($8 V) was estimated to be 1.94 Â 10 À9 %. Light output powers for the Si NC LEDs with SiC and SiN x films were almost same, which was around 0.3 nW at an input current of 20 mA. Since the forward voltage of the Si NC LED with a SiN x film was around 12.5 V at an input current of 20 mA, the input power of the Si NC LED with a SiN x film was then increased by 56% compared to the Si NC LED with a SiC film, resulting in a decrease in the WPE by 56%. Inset shows the optical microscope image of light emission from the Si NC LED measured at a forward voltage of 12 V. Because the EL peak had a relatively broad spectrum (shown in Fig. 4(a)), we think that the Si NC LED measured at voltage of 12 V showed the white light emission (shown in the inset in Fig. 4(b)). The uniformity of light emission was quite good. Based on the result of the electrical and light output performances, it was concluded that the SiC film could lead to realize an efficient Si NC LED compared to a SiN x film as a surrounding matrix including the Si NCs.In summary, a strong visible electroluminescence from Si NCs embedded into a SiC film was demonstrated. Compared to the Si NC LED by employing the SiN x film, the electrical characteristics of the Si NC LED with the SiC film were significantly improved. This was originated from a smaller barrier height for injecting the electrons into the Si NCs due to a smaller band gap of the SiC film than the SiN x film. Moreover, WPE of the Si NC LED with the SiC film was enhanced by 56% compared to that of the Si NC LED with the SiN x film. The light emission originated from the Si NCs in the SiC film was quite uniform. The results presented here can provide a very promising way to significantly improve the performance of Si NC LED.

Self-Etching-Induced Morphological Evolution of ZnO Microrods Grown on FTO Glass by Hydrothermal Method

“…In order to identify the facets of the remaining surfaces, the six smooth prismatic side planes of the rods are identified according to K. S. Chen et al [ 23 ]. They used H implantation and subsequent high temperature annealing on ZnO surface to determine the relative surface formation energies and to construct a Wulff plot.…”

“…3g , g' , the 12 tilt surfaces can be divided into six groups belonging to six <1 10> directions. Again K. S. Chen et al [ 23 ] have reported the surface formation energy of ZnO nanowire with zone axis along [1 10]. Their data show that the most stable facets are ( 014) and (10 4).…”

Clustered vacancies in ZnO: chemical aspects and consequences on physical properties

“…Chen et al also identified 17 clustering of several (4)(5)(6) VZnVO divacancies from the measured value of PAL in Al irradiated ZnO. Agglomeration of VZn and VO defects (in general (VZn)m (VO)n type with m ≈ n) during annealing (at relatively lower temperature 23 ) or by multiple collision cascades of energetic ions may lead to nano-voids in the system 24,25 . From surface energy consideration, if two open volume defects with similar radii coalesce to a form larger one, energy is lowered roughly by 20%.…”

Formation of N2 bubbles along grain boundaries in (ZnO)1−x(GaN)x: nanoscale STEM-EELS studies

“…In particular, the O-terminated internal polar facets are more stable than the Zn-terminated, in agreement with previous observations. 22 This polar facet disappears as the voids grow in size and finally only the semi-polar facets prevail. This is in agreement with calculations showing that the polar planes in ZnO exhibit higher surface formation energy compared to the non-polar planes.…”