O-vacancies in (i) nanocrystalline HfO2 and (i) noncrystalline SiO2 and Si3N4 studied by x-ray absorption spectroscopy

Defect States below the Conduction Band Edge of HfO2 Grown on InP by Atomic Layer Deposition

“…All 12 peaks were detected and are composed of six terms: three singlets and three triplets represented by group theory and multiplet theory. (The energy ordering in increasing energy is 3 F, 3 P, 1 G, and 1 S.) ,, This result is in good agreement with previous reports and can be explained by C-F splitting and J–T distortions . During film deposition or post-deposition annealing (PDA), the HfO 2 film is crystallized and, in this state, may still contain a significant concentration of oxygen vacancies.…”

“…In this process, degenerated energy bands of 3 F and 3 P triplets were separated and 12 different energy levels were evident by degeneracy removal by C-F splitting and J–T distortion, as shown in Figure a. The negative ion states are caused by an atomic properties, not ligand-field-defined properties . Figure b displays the oxygen vacancy induced by the absorption states within the band gap of the t -HfO 2 (∼5.8 eV) with the three singlet negative ion states near the CBE.…”

“…HfO 2 with a high dielectric constant (κ) is considered to be one of the most promising candidates for replacing SiO 2 , and mass production has already been implemented . Recent research on HfO 2 gate oxide materials has focused on dielectric properties, thermal stability, and suitable band offsets with III–V channel materials. − The dielectric properties of HfO 2 for MOS devices are strongly affected by their crystallinity, uniformity, and the extent of defect formation in the gate oxide. The crystallinity of a HfO 2 gate oxide can have an influence on capacitance accumulation; at the same gate oxide thickness, tetragonal ( t ) HfO 2 has a higher accumulation capacitance than monoclinic ( m ) HfO 2 due to the higher permittivity of t -HfO 2 than that of m -HfO 2 .…”

“…The other origin is that the gap states result from the oxygen vacancies, oxygen interstitials, III–V dangling bonds, and III–V dimer pairs . These defect states in HfO 2 reduce a band gap; Lucovsky et al reported that negatively charged O-atom vacancies in nanocrystalline transition-metal (TM) oxides induce defect states near the conduction band edge (CBE) of t -HfO 2 , thus resulting in a decrease in band gap . In addition, our previous study using an HfO 2 /InP system showed that the formation of O-atom vacancies in HfO 2 accelerates both the out-diffusion of InP substrate elements and an increase in midgap defect density on the order of ∼10 13 cm –2 .…”

Carrier Mobility Enhancement of Tensile Strained Si and SiGe Nanowires via Surface Defect Engineering

“…A change in defect states can be also observed in O K-edge spectra. In Figure b, O K-edge spectra of an as-grown Si NW show that the states of the conduction band edge related to surface defects (indicated by an arrow) were obviously formed but were significantly decreased after passivation. − However, in the as-grown SiGe NW, the defect states at the NW surface were decreased substantially, compared to that of Si NW. Moreover, the defect states were also decreased slightly after passivation.…”