Microstructural evolution during epitaxial growth of Ag on vicinal InP(100) surfaces

Abstract

The initial stages of epitaxial growth of Ag on InP(100) have been studied using in situ and ex situ electron microscopy. Vicinal InP substrates were cleaned by heating to about 400 °C in ultrahigh vacuum. Silver was deposited at substrate temperatures between 350 and 500 °C. The microstructural evolution was monitored for coverage between 0.5 and 8 monolayers using in situ high spatial resolution secondary electron microscopy and ex situ plan-view transmission electron microscopy (TEM). At sub-monolayer coverage, uniform, faceted islands of Ag are formed with edges aligned along InP 〈110〉 directions. Continued deposition leads to growth of preexisting islands followed by coalescence. During coalescence, a reduction in the island height, an increase in island-substrate interfacial area, and a disappearance of faceting are observed. At high coverage, during high temperature (450 °C) growth, the formation of faceted pits are observed. For higher temperatures (500 °C) and at low coverage, islands transform from square to rectangular shapes. Plan-view TEM indicates that the smallest Ag islands (∼5 nm) are not coherent with the substrate and that there are two distinct epitaxial relationships between the Ag islands and the InP substrate. For high-temperature growth, the (110)Ag plane is parallel to InP(100) substrate and there is evidence for chemical reaction and presence of In on the surface. For lower temperature depositions (350–400 °C), the (100)Ag is parallel to (100) InP.

The MIDAS project at ASU: John Cowley's vision and practical results

“…Another student, Yun Li, also worked with us on Ge/Si(100) in the early 90's, though not on MIDAS, and reminded us that not all surface work requires a microscope; in her case she used AES on Si/Ge/Si(100) sandwich structures to determine the segregation energy of Ge at the surface of Si(100) to be 0.24 ± 0.02 eV [44,45], very close to that subsequently calculated by others [46]. In the same time period, Krishamurthy and Drucker used MIDAS to extend their interest in related systems by exploring Ag/GaAs(110) [47] and Ag/InP(100) [48] for comparison with Ag/Si(100). Jeff Drucker, who returned to ASU as a faculty member in 2000, has made the Ge/Si system his own, with extensive work on the growth, inter-diffusion and properties of quantum dots [49] using many techniques, but especially atomic force microscopy (AFM) in conjunction with HREM and EELS.…”