ATOMIC IMAGING, ATOMIC PROCESSING AND NANOCHARACTERIZATION OF CUINSE2USING PROXIMAL PROBE TECHNIQUES

Defects play a dominant role in the determination of the electro-optic al properties of single-crystal and polycrystalline CuInSe2. This pape r examines the fundamental nature of point and grain boundary defects in this Cu-ternary semiconductor and, for the first time, provides dir ect evidence underlying the defect chemistry. Special scanning probe m icroscopy (SPM) techniques are used for real-time atomic imaging, atom ic processing (single-atom manipulation), and nanoscale characterizati on of the same regions of the sample. The (220)-tri-elemental, p-rype surfaces are examined and imaged. Cu-, In-, and Se-vacancies are creat ed using combined, pulsed electric (SPM tip-surface), and single-wavel ength photon fields for selected, single-atom removal. The electro-opt ical characteristics of these defects (before and after creation) are examined using SPM-based nano-photoluminescence and nano-cathodolumine scence techniques that provide information in the same nanometer regim e. Bulk photoluminescence spectra are compared and interpreted with re spect to these data that give first time direct, atomic-level correlat ions. In addition, the healing of these point defects by the placement of single intrinsic atoms of the same type at the vacancy sites is ac complished using the atomic processing techniques. The electronic defe ct levels are verified and correlated with the atomic-scale observatio ns. Finally, donor and acceptor defects, Cu and Se vacancies, Cu at In sites (Cu(In)) and Se at Cu sites (Se(Cu)), are created, evaluated, a nd characterized. The placement of the acceptor heteroimpurity oxygen at Se vacancies is also examined. This is done both at isolated Se vac ancies and at vacancies along electronically active grain boundaries. The passivation of these regions (by p-type doping of the grain bounda ry) is evaluated using nanoscale electron-beam induced-current (NEBIC) , and newly-developed, SPM-based minority-carrier spectroscopy techniq ues. This paper reports, for the first time, the engineering of these defects on the atomic scale, and complements these results with the di rect evaluation of the atomic manipulations using nanoscale electro-op tical characterization methods.