Epitaxial growth of rhombohedral β- and cubic γ-CuI

Isolated small crystals and closed epitaxial layers of CuI could be deposited on various substrates by close distance sublimation (CDS). X-ray diffraction measurements and detailed TEM studies revealed phase pure cubic gamma -CuI (zincblende structure) layers and a combination of a CuI multilayer structure with gamma -CuI. The multilayer structure, a 12R polytype with the space group R3m, the lattice parameters a0 = 0.4279 nm, c0 = 4.25 nm, and a twelve layers array consisting of wurtzite-like and zincblende layer sequences in combination with gamma -CuI could be detected. The presence of the polytype phase was detected always together with gamma -CuI. The epitaxial relationships between the CuI phases and various substrates are discussed. Low temperature (2 K) photoluminescence spectra of phase-pure gamma -CuI layers show typical excitonic emission spectra in the range between 3.0 and 3.1 eV. Samples containing both, the 12R polytype and gamma -CuI, additionally reveal a predominant series of intense emission lines around 3.25 eV attributed to excitonic emission from the rhombohedral phase.

Automated summary

Using close distance sublimation (CDS), isolated small crystals and closed epitaxial layers of CuI were successfully deposited on various substrates. X-ray diffraction and TEM studies revealed phase-pure CuI layers with a combination of CuI multilayer structure and γ-CuI. The low temperature (2 K) photoluminescence spectra of phase-pure γ-CuI layers showed typical excitonic emission spectra, while samples containing both the 12R polytype and γ-CuI revealed intense emission lines attributed to excitonic emission from the rhombohedral phase around 3.25 eV.