Morphology Of Epitaxial Films Research Articles

Weak Epitaxy Growth of Phthalocyanine on 2,5-Bis(4-1,1′:4′,1′′-terphenyl)-thiophene and the Effect of Phase State of Inducing Layer

The growth of ultrathin films of 2,5-bis(4-1,1':4',1''-terphenyl)-thiophene (3PT) and weak epitaxy growth (WEG) behavior of phthalocyanines (H(2)Pc and ZnPc) on 3PT ultrathin films were investigated by atomic force microscopy, X-ray diffraction (XRD), and select area electron diffraction (SAED). Domain size of the monolayer films can reach 10 μm at the substrate temperature of 190 °C. The second layer films begin to show Volmer-Weber growth mode. This growth mode transformed without a concomitant phase transition. The XRD and SAED measurements indicate the monolayer and double-layer films of 3PT have identical in-plane and out-of-plane structure. The epitaxial ZnPc films have a similar orientation or intertexture shape utilizing 3PT monolayer and double-layer films as the inducing layer. By comparison with utilizing para-sexiphenyl (p-6P) as the inducing layer, the morphology with clear borderline of epitaxial films with different orientations on joint of neighboring 3PT monolayer domains disclosed that the 3PT monolayer films have characteristics of crystal. Meanwhile the distinguishing effects of inducing layer phase state on morphology of epitaxial films were shown, respectively.

Electron-beam-induced modification of PbSnTe surface morphology under HEED monitoring of MBE growth

An AFM investigation is conducted into the effect of an electron beam on the surface morphology of PbSnTe films under HEED monitoring of MBE growth. The films are grown on a Si(100) substrate provided with a BaF2/CaF2 buffer. The electron beam is shown to degrade the surface morphology of epitaxial films, changing irregularity shape and size considerably. It is concluded that HEED patterns can be misleading about MBE growth.

Atomic Force Microscopy Study of GaN Grown on Al2O3(0001) by LP-MOVPE

ABSTRACTThere is currently a high degree of interest in understanding the diverse mechanisms that determine the growth morphology of epitaxial films. To understand and control over these mechanisms, it is essential to know how the growth mechanisms are correlated with morphologies. In GaN MOVPE processes, growth temperature has a remarkable effect on the film morphologies and properties. In present work, the temperature dependency of surface morphology of GaN epilayers grown by low-pressure metal-organic vapor phase epitaxy (LP-MOVPE) was studied using atomic force microscopy. It was demonstrated that dislocations strongly influence the growth mechanisms and the morphology of the films. Three growth modes were identified at different growth temperature ranged from 1030°C to 1100°C, which are, (1) spiral growth dominated by dislocation with screw type, (2) monolayer step flow, and (3) nucleation-assisted step flow growth. The significant effect of dislocation on the surface morphologies and growth mechanisms may be attributed to the high dislocation density and higher activation energy for a step overcoming the dislocation pinning in GaN. Because few dislocations will be introduced under monolayer step flow growth mode, we can infer the useful information about GaN initial growth.

Surface morphology of silicon carbide epitaxial films

Silicon carbide (SiC) semiconductor technology has been advancing rapidly, but there are numerous crystal growth problems that need to be solved before SiC can reach its full potential. Among these problems is a need for an improvement in the surface morphology of epitaxial films that are grown to produce device structures. Because of advantageous electrical properties, SiC development is shifting from the 6H to the 4H polytype. In this study of both 6H and 4H-SiC epilayers, atomic force microscopy and other techniques were used to characterize SiC epilayer surface morphology. Observed features included isolated growth pits a few micrometers in size in both polytypes and triangles (in 4H only) approximately 50 um in size for epilayers 3 um in thickness. Also observed in some epilayers were large steps with heights greater than 20 nm. We found that there are significant differences between the morphology of 6H and 4H epilayers grown under identical conditions. We were able to improve surface morphology by avoiding conditions that lead to excess silicon during the initial startup of the growth process. However, the observed morphological defect density in both 6H and 4H epilayers was still the order of 104 cm-2 and varied widely from run to run. As expected, we found that morphological defects in the SiC substrates play a role in the formation of some epilayer surface features.

Photo-Assisted Molecular Layer Epitaxy

ABSTRACTPhotoexcitation effects of GaAs vapor phase epitaxy have been studied. The growth rate is enhanced by irradiating the substrate zone with an exciier laser irradiation at 2 4 9 n m wavelength, however, the growth rate is reduced by irradiating the source Ga zone with a 249 or 222m exciier laser at températures below 650*C. Because of sharp wavelength dependence and from the result of the theoretical estimations, these effects have been concluded to be caused not by a therma1 -induced reaction but, rather, by photoinduced reactions.Influence of photoexcitation of the film grown by molecular layer epitaxy has been also studied. Photoirradiation could be independently undertaken at different crystal growth steps, e.g. the irradiation duration could be synchronized with the time duration of each gases supply and exhaust. By this method “synchronized irradiation”, the quality of the epitaxial film and the surface morphology of epitaxial films grown by molecular layer epitaxy were improved.