Oriented Attachment: A Path to Columnar Morphology in Chemical Bath Deposited PbSe Thin Films

We have studied columnar PbSe thin films obtained using chemical bath deposition. The columnar microstructure resulted from an oriented attachment growth mechanism, in which nuclei precipitating from solution attached along preferred crystallographic facets to form highly oriented, size-quantized columnar grains. This is shown to be an intermediate growth mechanism between the ion-by-ion and cluster growth mechanisms. A structural zone model depicting the active growth mechanisms is presented for the first time for semiconductor thin films deposited from solution. The columnar films showed well-defined twinning relations between neighboring columns, which exhibited 2D quantum confinement, as established by photoluminescence spectroscopy. In addition, anisotropic nanoscale electrical properties were investigated using current sensing AFM, which indicated vertical conductivity, while maintaining quantum confinement.