Abstract
A porous layer containing interconnecting network of nanofibersis known to be formed in GaSb under irradiation of ion beamshaving energy varying from tens of keV to a few MeV. Earlierstudies on such structural modifications of GaSb were focusedon the low fluence range (up to ~1??10^16 ions cm^-2). Theevolution of nanofibrous layer in the high fluence regime hasremained unexplored although in addition to understanding themicrostrcutural development, this regime is also important inthe context of self-organized surface patterning under irradiation.In the present study we show that normally and obliquely incident(theta = 60^0) 60 keV Ar^+ -ion irradiation of GaSb in the fluencerange 7??10^16 -3??10^18 ions cm^-2 demonstrates hitherto unobservedstructural modifications. In particular, we find obliquely incidentirradiation induced formation and gradual embedding of thenanofibrous layer under a rough top surface. In addition, theirradiation results in simultaneous formation of an undulatinginterface of the nanofibrous layer with the underlying GaSbcrystalline substrate. The observed structural evolution isunderstood in terms of redeposition of sputtered atoms-from Ar-ionbombarded GaSb-onto the nanofibrous layer growing byaccumulation of ion induced vacancies. We further address theissues of the crystallinity and compositional modifications of thenanofibrous layer under such high fluence irradiation. Finally,as further exploration of high fluence induced evolution of ananofibrous layer, we present the structural modification in InSbunder similar experimental conditions, namely, under normally andoff-normally (theta = 60^0) incident 60 keV Ar^+ -ion bombardmentin the fluence range of 1??10^17 – 3??10^18 ions cm^-2.
