Band alignment of vanadium oxide as an interlayer in a hafnium oxide-silicon gate stack structure

Abstract

Vanadium oxide (VO2) is a narrow band gap material (Eg = 0.7 eV) with a thermally induced insulator-metal phase transition at ∼343 K and evidence of an electric field induced transition at T < 343 K. To explore the electronic properties of VO2, a sandwich structure was prepared with a 2 nm VO2 layer embedded between an oxidized Si(100) surface and a 2 nm hafnium oxide (HfO2) layer. The layer structure was confirmed with high resolution transmission electron microscopy. The electronic properties were characterized with x-ray and ultraviolet photoemission spectroscopy, and the band alignment was deduced on both n-type and p-type Si substrates. The valence band offset between VO2 and SiO2 is measured to be 4.0 eV. The valence band offset between HfO2 and VO2 is measured to be ∼3.4 eV. The band relation developed from these results demonstrates the potential for charge storage and switching for the embedded VO2 layer.

Hybrid band offset calculation for heterojunction interfaces between disparate semiconductors

“…Although they also reported the 3.4 eV VBO in the HfO 2 /VO 2 /HfO 2 film, this arises from the different configuration and the interfacial dipole has affected the band edge line-up. 18 Ramanathan et al fabricated GaN/VO 2 p-n heterojunctions with a CBO of $0.8 eV by I-V and C-V measurements, 15 resembling to our calculated CBO of 0.6 eV. Pickett used the LDAþU method on the TiO 2 /VO 2 interface, 39 and the calculated VBO (1.0 eV) is the same as our data.…”

“…13 These devices have an interface between VO 2 and a semiconductor like GaN, [14][15][16] a substrate like TiO 2 , 13 or a gate insulator like HfO 2 . 17,18 The electronic structure of VO 2 can be described by methods such as GW or cluster-dynamic mean field theory (c-DMFT). 19,20 On the other hand, hybrid functionals describe many aspects of its electronic structure within band theory at a relatively low cost.…”

“…However, most of the studies on dielectric/VO 2 interfaces concern the phase transition stability and electronic characteristics, 13 and only a few focus on the band alignments. 15,17,18 A brief comparison with the limited reports is summarized in Fig. 4 (green bars).…”

Band alignment calculation of dielectric films on VO2

“…Dielectric films such as Al 2 O 3 [13,14] and TiO 2 [15] have been deposited on VO 2 to study the phase transition stability and electronic characteristics. Nemanich et al utilized VO 2 as an interlayer in a HfO 2 -Si gate stack and a HfO 2 -VO 2 -HfO 2 confined well structure to study the band alignment [16,17]. Besides, highquality VO 2 films can be epitaxially growth on TiO 2 substrate by pulsed laser deposition, and tune the MIT transition by interfacial strain engineering [18].…”

Reexamination of band offset transitivity employing oxide heterojunctions

“…The experimental core-level binding energies obtained in our work are $3 eV smaller than the published values. 10,11 And this is due to the charging effect. The XPS measurement was carried out by Thermo Scientific ESCALAB 250Xi.…”