Atomic and electronic structure of amorphous and crystalline hafnium oxide: X-ray photoelectron spectroscopy and density functional calculations

Перевалов, Т. В.; Gritsenko, V. V.; Эренбург, С. Б.; Badalyan, A. M.; Wong, Hei; Kim, C. W.

doi:10.1063/1.2464184

Cited by 88 publications

(48 citation statements)

References 27 publications

(31 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This is justified because on a crude level the electronic properties of the two phases are qualitatively similar. In particular, the calculated band gaps (3.8eV for the fluorite and 4.0eV for the monoclinic phase, the experimental value being 5.7eV [26,32]) and valence band widths (6.5eV for the fluorite and 5.6eV for the monoclinic phase) are quite similar.The Hf atoms occupy an fcc sublattice in the fluorite phase. A simple cubic supercell was chosen containing four Hf and eight O sites, and one of the four Hf atoms was replaced by Gd.…”

mentioning

confidence: 49%

The n-type Gd-doped HfO2 to silicon heterojunction diode

et al. 2007

View full text Add to dashboard Cite

Gd-doped HfO 2 films were deposited on p-type silicon substrates in a reducing atmosphere. Photoemission measurements indicate the ntype character of Gd-doped HfO 2 due to overcompensation with oxygen vacancies. The Gd 4 f photoexcitation peak at 5.5 eV below the valence band max imum is identified using both resonant photoemission and first-principles calculations of the f hole. The rectifying (diode-like) properties of Gd-doped HfO 2 to silicon heterojunctions are demonstrated.PACS 68.55.Ln; 29.40.Wk; 81.05.Je ________________________________________ While HfO 2 has attracted considerable attention as a high-κ dielectric oxide [1][2][3][4], the gadolinium doping of a number of wide band gap semiconductors [5][6][7][8][9] suggests that Gd doping of HfO 2 may also lead to a dilute magnetic semiconduc tor [10,11]. Moreover, semiconducting Gd-doped HfO 2 may provide a promising new class of materials for neutron detec tion technologies.A gadolinium-based semiconductor diode might be better for neutron detection because of the large thermal neutron absorption cross section of gadolinium (on average ~ 46,000barns). The 157 Gd(n,γ)→ 158 Gd and 155 Gd(n,γ)→ 156 Gd reactions lead to the emission of low-energy gamma rays and conversion electrons, most of which are emit ted at energies below 220 eV [12][13][14][15]. The appeal of using 157 Gd is due to its large thermal neutron cross section of 240 000 barns [16,17]. Although sensitive to gamma radia tion, the big advantage of gadolinium over boron is not only the high neutron capture cross section but also that this cross section extends to higher neutron energies (200 meV)thanis the case for boron. While all-boron-carbide neutron detectors have been demonstrated [18][19][20], and their potential detection efficiency is much higher than that of many semiconductor materials (likely well above 50% for 10 B-enriched devices), the drawback to all boron-based devices is the need for a mod erator to reduce the neutron kinetic energies to 25-30 meV. Fissile radiation sources like 235 U or 239 Pu produce 1-2MeV neutrons, so the moderator must be significant.Since neutron capture by gadolinium leads to production of a conversion electron, the pulse height will be smaller than in the case of neutron capture by boron (10 4 charges versus 10 6 per neutron capture). Accordingly, it is advantageous to see if a Gd-doped HfO 2 diode can be fabricated that can be impedance matched and compatible with a high gain, low noise amplifier. A heterojunction diode with silicon would serve this purpose. Although Gd is expected to be a p-type dopant in HfO 2 , we attempted to fabricate a heterojunction diode of n-type Gd-doped HfO 2 with silicon by overcompen sating the Gd acceptor states by donor states introduced by oxygen vacancies, as such a device would likely have a larger depletion region and therefore larger detection volume.The Gd-doped (3 at. %) HfO 2 films were deposited on single crystal silicon (100) p-type substrates using pulsed laser deposition (PLD) at a growth rate of a...

show abstract

mentioning

confidence: 49%

The n-type Gd-doped HfO2 to silicon heterojunction diode

et al. 2007

View full text Add to dashboard Cite

show abstract

“…One of the reasons is the difficulties in generating reasonable and reliable amorphous structures with the available theoretical methods. Experimentally, the high-κ materials are deposited on silicon substrate by vapor deposition (as-deposited films) followed by annealing processes at around 1000 K. 13,14 Simulating the deposition process and the resulting amorphous high-κ material structures by molecular dynamics (MD) is extremely time consuming because the deposition rate must be controlled close to the experimental value that is usually very low. The as-deposited a-HfO 2 and a-Al 2 O 3 films have been generated by kinetic Monte Carlo (KMC) methods 6,15 with certain assumptions such as the atoms are kept fixed on pre-determined crystal sites and less important dynamics processes of atomic motion are omitted.…”

Section: Introductionmentioning

confidence: 99%

Structure and dielectric properties of amorphous high-κoxides: HfO2, ZrO2, and their alloys

et al. 2012

View full text Add to dashboard Cite

High-κ metal oxides are a class of materials playing an increasingly important role in modern device physics and technology. Here we report theoretical investigations of the properties of structural and lattice dielectric constants of bulk amorphous metal oxides by a combined approach of classical molecular dynamics (MD) -for structure evolution, and quantum mechanical first principles density function theory (DFT) -for electronic structure analysis. Using classical MD based on the Born-Mayer-Buckingham potential function within a melt and quench scheme, amorphous structures of high-κ metal oxides Hf1−xZrxO2 with different values of the concentration x, are generated. The coordination numbers and the radial distribution functions of the structures are in good agreement with the corresponding experimental data. We then calculate the lattice dielectric constants of the materials from quantum mechanical first principles, and the values averaged over an ensemble of samples agree well with the available experimental data, and are very close to the dielectric constants of their cubic form.

show abstract

“…However, for the dielectric film with 0.5 nm EOT, the physical thickness should be in the range of 2-3.5 nm, which is again in the direct tunneling (DT) limit [60]. Note that, because of smaller band offsets and larger effective masses [61], the direct tunneling can occur across much thicker films. Table 1 lists the parameters governing electrical conduction for HfO 2 and La 2 O 3 .…”

Section: Subnanometer Eot Leakage Current and High-k Instabilitiesmentioning

confidence: 99%

“…Most of the high-k silicides are conductive. The interfacial silicide layer would not affect the EOT but the interface metal-Si bonding is one of the interface trap precursors and results in the channel mobility degradation and in other instabilities [2,[59][60][61][62][63][64][65][66][67][68][69][70]. Most of the high-k materials, including hafnium oxide and lanthanum oxide are only marginally stable against the formation of silicates.…”

Section: Lanthanum Oxide/silicon Interfacementioning

confidence: 99%

“…It was proposed that the oxygen in W may diffuse into the La 2 O 3 film to fill up the oxygen vacancies there. Oxygen vacancies are the major defect centers in La 2 O 3 which result in several instability issues and enhance the gate leakage current [59][60][61][62][63][64][65][66][67][68][69][70][71]. Post-metallization annealing may cause an reverse effect.…”

Section: Lanthanum Oxide/metal Gate Interfacementioning

confidence: 99%

See 1 more Smart Citation