Submicron rectangular hollow tube crystals of rutile-type GeO_2

摘要

Single crystals of rutile-type GeO_2 having a structure equivalent to that of TiO_2, a well-known photocatalyst, have been grown for the first time in supercritical oxygen at approximately 5 Gpa and 3000 K. The obtained crystals exhibit a rectangular hollow tube structure with submicron size (cross section with sides of ～500 nm, wall thickness of ～20 nm, and longitudinal length of ～5 μm). These single crystals were grown within 1 s and along the c-axis surrounded by the (110) faces. The crystal growth mechanism strongly depends on the growth mechanism of rutile-type oxides, and the extremely short growing time is an important factor in the formation of hollow tube crystals.