Jae Jin Yoon

Effect of annealing temperature on microstructural evolution and electrical properties of sol-gel processed ZrO2/Si films

High-permittivity (k) ZrO2/Si(100) films were fabricated by a sol-gel technique and the microstructural evolution with the annealing temperature (Ta) was correlated with the variation of their electrical performance. With increasing Ta, the ZrO2 films crystallized into a tetragonal (t) phase which was maintained until 700 °C at nanoscale thicknesses. Although the formation of the t-ZrO2 phase obviously enhanced the k value of the ZrO2 dielectric layer, the maximum capacitance in accumulation was decreased by the growth of a low-k interfacial layer (IL) between ZrO2 and Si with increasing Ta. On the other hand, the gate leakage current was remarkably depressed with increasing Ta probably due to the combined effects of the increased IL thickness, optical band gap of ZrO2, and density of ZrO2 and decreased remnant organic components.

InAs critical-point energies at 22 K from spectroscopic ellipsometry

We report dielectric function data from 0.74 to 6.54 eV for InAs at 22 K, obtained by spectroscopic ellipsometry. Critical-point (CP) structures are blueshifted and significantly sharpened relative to those seen at room-temperature (RT). The E0′, E2Δ, E2, E0′+Δ0′, and E2′ features in the E2 energy range of 4.0 to 5.6 eV cannot be resolved at RT but are clearly separated at 22 K. The energies of the CPs giving rise to these structures are determined by line shape fitting to numerically calculated second energy derivatives, and their Brillouin-zone locations identified by band structure calculations using the linear augmented Slater-type orbital method.

Optical study of sol-gel processed ZrO2/Si films by spectroscopic ellipsometry

We report optical properties of amorphous and tetragonal ZrO2 films grown on Si substrates by sol-gel deposition and formed by annealing at different temperatures. Pseudodielectric-function spectra ⟨e⟩ from 1.12 to 6.52 eV were acquired by spectroscopic ellipsometry at angles of incidence of 50, 55, 60, 65, and 70° with the samples at room temperature, then analyzed with the Tauc–Lorentz (TL) model for the refractive index and extinction coefficient of the films. These depend significantly on annealing temperature, and consistent with X-ray diffraction data, showing that amorphous ZrO2 crystallizes into the tetragonal phase between 300 and 500 °C, and that it coexists with the monoclinic phase after annealing at 700 °C. The dielectric functions of these materials can be calculated analytically within this spectral range from the TL parameters given.We report optical properties of amorphous and tetragonal ZrO2 films grown on Si substrates by sol-gel deposition and formed by annealing at different temperatures. Pseudodielectric-function spectra ⟨e⟩ from 1.12 to 6.52 eV were acquired by spectroscopic ellipsometry at angles of incidence of 50, 55, 60, 65, and 70° with the samples at room temperature, then analyzed with the Tauc–Lorentz (TL) model for the refractive index and extinction coefficient of the films. These depend significantly on annealing temperature, and consistent with X-ray diffraction data, showing that amorphous ZrO2 crystallizes into the tetragonal phase between 300 and 500 °C, and that it coexists with the monoclinic phase after annealing at 700 °C. The dielectric functions of these materials can be calculated analytically within this spectral range from the TL parameters given.

Optical properties of solution-processed LaAlOx/Si films using spectroscopic ellipsometry

The dielectric functions, e, of amorphous LaAlOx (LAO) films grown by the sol–gel process are investigated using spectroscopic ellipsometry. The LAO precursor sols are prepared at a molar ratio of La:Al = 1:1 with different mole concentrations to control the film thickness. The films are deposited on p-type Si substrates treated with dilute HF, and the sols are sintered at 400 °C for 2 h in an ambient atmosphere. Room-temperature pseudodielectric function spectra, ⟨e⟩, are obtained from 0.7 to 8.6 eV, and best fits of the data are obtained with the Tauc–Lorentz (TL) model. The authors observe an increase in both the real and imaginary parts of e, a decrease in the TL threshold energy Eg, and an increase in film thickness with increasing mole concentration of the precursor solution.