In-Situ Investigation of Particle Assisted GaSb Nucleation Using Environmental TEM

Sammanfattning: III-V semiconductor material based nanowires have been extensively studied and shown to be a very exciting building block for future electronics. Material systems such as GaSb show a lot of promise in optoelectric and thermoelectric generation applications because of its high electron mobility and small bandgap. Although there is a lot of research about III-V nanowires, a gap in understanding antimony based nanowire growth is present. The surfactant effect of Sb makes growth of antimony based nanoowires challenging. The aim of this master thesis is to investigate direct nucleation of GaSb from both Au and Sn seed particles which would help to develop a method for direct nucleation. The study is carried out in an environmental transmission electron microscope which enables the nucleation of GaSb to be studied and recorded in-situ. Au seeded nucleation occurred at high amounts of Ga present in the particle, above 90 at.%, whilst it is shown that Sn seeded nucleation is possible for a very broad range of seed particle compositions, between 12 at.% and 70 at.%. The Au seeded nanowires were much bigger than the Sn seeded, 100 to 200 nm and 25 to 50 nm respectively, which is related to the Ga amount in the seed particle. This shows that Sn seeded GaSb direct nucleation gives much more promise if the nanowires would be integrated into electrical devices where smaller diameter nanowires are needed. For Au seeded GaSb nanowires twin planes were observed in the zinc blende crystal structure which indicated a possibility of polytypism in GaSb nanowires which has not been reported yet. The observation of polytypism in GaSb is the first step to crystal phase engineering in GaSb nanowires which could be crucial in applications such as nanowire quantum dot devices. This thesis serves as a guideline and a starting point for further GaSb direct nucleation, nanowire growth and crystal structure studies.