Aim To study the relationship between the substrate temperature and the morphology and properties of GaN. Methods\ Applying the hydride chemical vapor deposition method, GaN films were deposited on different kinds of...Aim To study the relationship between the substrate temperature and the morphology and properties of GaN. Methods\ Applying the hydride chemical vapor deposition method, GaN films were deposited on different kinds of substrates, including sapphire, Si(111),Si(100),GaAs and GaP(111) both on the P face and the Ga face. The growth was performed at low temperatures of below 700℃. XRD, Hall measurement, cathodoluminescence (CL) and atomic force microscopy (AFM) were used to characterise the film properties. Results\ It was found that the temperature and the nature of substrate materials influence the layer morphology. Conclusion\ The analysis shows that no apparent relationship exists between the optical properties and layer morphology.展开更多
Contacting mode atomic force microscopy (AFM) is used to measure the In 0.35 Ga 0.65 As/GaAs epilayer grown at low temperature (460℃).Unlike the normal layer by layer growth (FvdM mode) or self organized i...Contacting mode atomic force microscopy (AFM) is used to measure the In 0.35 Ga 0.65 As/GaAs epilayer grown at low temperature (460℃).Unlike the normal layer by layer growth (FvdM mode) or self organized islands growth (SK mode),samples grown under 460℃ are found to be large islands with atomic thick terraces.AFM measurements reveale near one monolayer high steps.This kind of growth is good between FvdM and SK growth modes and can be used to understand the evolution of strained epitaxy from FvdM to SK mode.展开更多
14H, 18R and 24R long-period stacking ordered （LPSO） structures were observed in the as-cast Mg-3Cu-1Mn-2Zn-1Y damping alloy using transmission electron microscopy （TEM）. These LPSO structures contained Mg, Y, Cu ...14H, 18R and 24R long-period stacking ordered （LPSO） structures were observed in the as-cast Mg-3Cu-1Mn-2Zn-1Y damping alloy using transmission electron microscopy （TEM）. These LPSO structures contained Mg, Y, Cu and Zn and thus they were quaternary phases. Sharp diffraction pattern of the 24R structure was obtained and the angle between and g10024R was measured to be 5.03°. During high resolution TEM observations, lattice fringes with two characteristic spacings were observed within the 24R structure. Based on the experimental results, 6H, 7H and three 8H are suggested as the building blocks of 18R, 14H and 24R structures, respectively. The 24R unit cell can be interpreted as the stacking of 8H building blocks in the same shear direction with a shear angle of about 5.03°. The imperfect 24R structures are in order or disorder arrangements of principal 8H and minor 6H blocks. This double-block structure model is also applicable to other reported defects in LPSO structures.展开更多
文摘Aim To study the relationship between the substrate temperature and the morphology and properties of GaN. Methods\ Applying the hydride chemical vapor deposition method, GaN films were deposited on different kinds of substrates, including sapphire, Si(111),Si(100),GaAs and GaP(111) both on the P face and the Ga face. The growth was performed at low temperatures of below 700℃. XRD, Hall measurement, cathodoluminescence (CL) and atomic force microscopy (AFM) were used to characterise the film properties. Results\ It was found that the temperature and the nature of substrate materials influence the layer morphology. Conclusion\ The analysis shows that no apparent relationship exists between the optical properties and layer morphology.
文摘Contacting mode atomic force microscopy (AFM) is used to measure the In 0.35 Ga 0.65 As/GaAs epilayer grown at low temperature (460℃).Unlike the normal layer by layer growth (FvdM mode) or self organized islands growth (SK mode),samples grown under 460℃ are found to be large islands with atomic thick terraces.AFM measurements reveale near one monolayer high steps.This kind of growth is good between FvdM and SK growth modes and can be used to understand the evolution of strained epitaxy from FvdM to SK mode.
基金Project (2009CB623704) supported by the National Basic Research Program of ChinaProject (50971076) supported by the National Natural Science Foundation of China
文摘14H, 18R and 24R long-period stacking ordered （LPSO） structures were observed in the as-cast Mg-3Cu-1Mn-2Zn-1Y damping alloy using transmission electron microscopy （TEM）. These LPSO structures contained Mg, Y, Cu and Zn and thus they were quaternary phases. Sharp diffraction pattern of the 24R structure was obtained and the angle between and g10024R was measured to be 5.03°. During high resolution TEM observations, lattice fringes with two characteristic spacings were observed within the 24R structure. Based on the experimental results, 6H, 7H and three 8H are suggested as the building blocks of 18R, 14H and 24R structures, respectively. The 24R unit cell can be interpreted as the stacking of 8H building blocks in the same shear direction with a shear angle of about 5.03°. The imperfect 24R structures are in order or disorder arrangements of principal 8H and minor 6H blocks. This double-block structure model is also applicable to other reported defects in LPSO structures.
