[Show abstract][Hide abstract] ABSTRACT: Jahn–Teller (J–T) term-split states in nanocrystalline transition metal and trivalent rare earth elemental and complex oxides reduce the band gap, and tunnelling barrier height at interfaces with crystalline Si substrates. These states are identified by x-ray absorption spectroscopy and spectroscopic ellipsometry. Alloys for suppression of J–T d-state degeneracy removal are identified as: (i) non-crystalline Zr/Hf silicates and Si oxynitrides and (ii) ZrO2–Y2O3 alloys with high concentrations of randomly distributed O-vacancies that promote cubic crystalline symmetry.
Radiation Physics and Chemistry 05/2007; · 1.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Spectroscopic studies, supported by theory indicate that neutral and negatively charged O-atom vacancies are the most important intrinsic defects in nanocrystalline thin films of Hf(Zr)O2. O-atom vacancy defects are identified in this paper by different spectroscopic technique: vacuum ultra-violet spectroscopic ellipsometry, near edge x-ray absorption spectroscopy, and cathodo-luminescence spectroscopy. O-vacancy defects are active as (1) interface traps for Si substrate injection of holes, and (2) bulk film traps for Si substrate injection of electrons. The markedly different electron and hole trapping properties are a potentially serious problem for threshold voltage control and stability in CMOS inverter FETs using nanocrystalline Hf(Zr)O2 dielectrics. O-vacancy defects are not observed spectroscopically in thermally and chemically stable Zr Si oxynitride alloy films, (SiO2)x(Si3N4)y(ZrO2)z, that have been annealed at 1100 C in Ar. Si3N4 concentrations in these alloys must be controlled within narrow limits, â0.36 to 0.4, with equal SiO2 and ZrO2 concentrations of approximately 0.32 to 0.3.
[Show abstract][Hide abstract] ABSTRACT: Defects ∼0.5–0.8 eV below the conduction band edge, contributing to trap-assisted tunneling and Frenkel–Poole transport have been reported for injection from n-type Si into SiO2–HfO2 dielectrics. Band edge spectroscopic measurements, combined with X-ray absorption spectroscopy, have identified localized defect states at this energy below the conduction band edges of HfO2, and ZrO2. Capacitance–voltage and cathodoluminescence studies, combined with band edge spectroscopy have identified an interfacial trap associated with oxygen atom vacancies as well.
Radiation Physics and Chemistry 01/2006; 75(11):2097-2101. · 1.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This paper uses X-ray absorption spectroscopy to study the electronic structure of the high-k gate dielectrics including TM and RE oxides. The results are applicable to TM and rare earth (RE) silicate and aluminate alloys, as well as complex oxides comprised of mixed TM/TM and TM/RE oxides. These studies identify the nature of the lowest conduction band d∗ states, which define the optical band gap, Eg, and the conduction band offset energy with respect to crystalline Si, EB. Eg and EB scale with the atomic properties of the TM and RE atoms providing important insights for identification high-k dielectrics that meet performance targets for advanced CMOS devices.