Unusual crystallographic structure and its fluctuation of indium nanoparticles as-deposited and observed with HRTEM using the UHV-DC-TEM system

A UHV-DC-TEM system was developed for direct transportation of samples between an ultra-high vacuum deposition chamber (UHV-DC) and a UHV transmission electron microscope (UHV-TEM). Indium nanoparticles have been deposited onto Si(110) TEM samples at room temperature in UHV-DC and observed in UHV-TEM with high resolution transmission electron microscopy (HRTEM). Freshly made indium nanoparticles were found to be single, twinned, pseudo-twinned crystals and decahedral multiply-twinned particles (MTPs) with their size in the range 8–15 nm. The structure of single crystalline indium nanoparticles is body-centered tetragonal (bct), which is the same as that of bulk indium. In addition to the usual {011} type twins for bct structure, a pseudo-twin was observed to have an orientation relationship as 111]_A//100]_B and (10 )_A//(0 )_B. The structure of MTP indium is complicated because of the co-existence of bct and fcc structures within one nanocrystal. The structure fluctuation process has been examined using a video recorder with time scale down to 1/60 s. No complete liquid state was seen during this fluctuation.