RESUMO
Doped ferroelectric HfO2 is highly promising for integration into complementary metal-oxide semiconductor (CMOS) technology for devices such as ferroelectric nonvolatile memory and low-power field-effect transistors (FETs). We report the direct measurement of the energy barriers between various metal electrodes (Pt, Au, Ta, TaN, Ti/Pt, Ni, Al) and hafnium zirconium oxide (Hf0.58Zr0.42O2, HZO) using internal photoemission (IPE) spectroscopy. Results are compared with valence band offsets determined using the three-sample X-ray photoelectron spectroscopy (XPS) as well as the two-sample hard X-ray photoelectron spectroscopy (HAXPES) techniques. Both XPS and IPE indicate roughly the same dependence of the HZO barrier on metal work function with a slope of 0.8 ± 0.5. XPS and HAXPES-derived barrier heights are on average about 1.1 eV smaller than barrier heights determined by IPE, suggesting the presence of negative charge in the HZO.
RESUMO
A novel atomic layer deposition (ALD) process for nickel oxide (NiO) is developed using a recently reported diazadienyl complex, Ni(tBu2DAD)2, and ozone. A window of constant growth per cycle is found between 185 and 200 °C at 0.12 nm/cycle, among the highest reported for ALD NiO. For films deposited at 200 °C, grazing-incidence X-ray diffraction indicates a randomly oriented polycrystalline cubic NiO phase. X-ray photoelectron spectroscopy shows good agreement with bulk NiO reference spectra and no detectable impurities. Atomic force microscopy reveals low root mean square roughness of 0.6 nm for an 18 nm thick film. The refractive index of 2.36 and an electronic bandgap of 3.78 eV, as determined by variable angle spectroscopic ellipsometry, are close to reported values for bulk and thin film NiO. Finally, fabricated Ag/NiO/n-Si/In heterojunction diodes show a current-voltage asymmetry of 1.27 × 104 at 2.3 V and an ideality factor of 3.5, confirming the intrinsic p-type semiconducting behavior of transparent NiO.
