Figure 3 - uploaded by G.-M. Rignanese
Content may be subject to copyright.
![Dielectric constants ( ∞ and 0 ) as a function of composition x for amorphous (ZrO 2 ) x (SiO 2 ) 1−x. The hatched region corresponds to results derived from the model scheme and reflects the indetermination of the number of ZrO 6 units. The upper curve delimiting the band corresponds to structures entirely composed of ZrO 6 units, while the lower curve represents a smooth transition from a structure composed of ZrO 4 units at x = 0 to one composed of ZrO 8 units at x = 0.5, without the occurrence of any ZrO 6 unit. The references for the experimental data are: [74], • [72], • [73], [68, 69], [75], [76], and [49].](profile/G-M-Rignanese/publication/230675862/figure/fig2/AS:669996296466440@1536750973525/Dielectric-constants-and-0-as-a-function-of-composition-x-for-amorphous-ZrO-2-x.png)
Dielectric constants ( ∞ and 0 ) as a function of composition x for amorphous (ZrO 2 ) x (SiO 2 ) 1−x. The hatched region corresponds to results derived from the model scheme and reflects the indetermination of the number of ZrO 6 units. The upper curve delimiting the band corresponds to structures entirely composed of ZrO 6 units, while the lower curve represents a smooth transition from a structure composed of ZrO 4 units at x = 0 to one composed of ZrO 8 units at x = 0.5, without the occurrence of any ZrO 6 unit. The references for the experimental data are: [74], • [72], • [73], [68, 69], [75], [76], and [49].
Source publication
A review is given of various first-principles studies of the dielectric properties of crystalline and amorphous transition metal oxides and silicates, which have drawn considerable attention as potential high-κ materials. After a brief summary of the principal equations of density-functional theory related to the dielectric properties of solids, th...
Contexts in source publication
Context 1
... this case, the effect of Zr coordination is negligible since the various Zr-centred units have close α values compared to SiO 4 (table 7). As plotted in figure 3, the theoretical values [8] agree very well with available experimental data [73,74]. ...
Context 2
... EXAFS measurements [70] tend to show that the average Zr coordination increases from about four to about eight for Zr concentrations increasing from x ∼ 0 to x ∼ 0.5. In figure 3, the calculated 0 for amorphous (ZrO 2 ) x (SiO 2 ) 1−x as a function of x [8] is plotted together with the available experimental data [68,69,72,73,75]. ...
Context 3
... characteristic parameters used to calculate 0 change noticeably with the local environment of Zr atoms. Therefore, the indetermination with respect to their coordination leads to a range of possible values for the theoretical values as represented by the dashed band in figure 3. Several suitable distributions of three representative structural units (ZrO 4 , ZrO 6 , and ZrO 8 ) have been considered [8]. ...
Context 4
... the indetermination with respect to their coordination leads to a range of possible values for the theoretical values as represented by the dashed band in figure 3. Several suitable distributions of three representative structural units (ZrO 4 , ZrO 6 , and ZrO 8 ) have been considered [8]. The upper curve delimiting the band in figure 3 corresponds to structures entirely composed of ZrO 6 units. The lower curve is for amorphous systems which do not contain any ZrO 6 units. ...
Context 5
... earlier data [68,69,75] cannot be explained. Figure 3 shows that, for a sufficient amount of ZrO 6 units, values of 0 at intermediate x can indeed be larger than estimated from a linear interpolation between SiO 2 and ZrSiO 4 . However, in agreement with recent experiments [72,73], the theory indicates that the extent of this effect is more limited than previously assumed [68][69][70]. ...
Similar publications
The effects of ion irradiation in the ABO4-type compounds were compared by performing experiments on four materials that include the most common crystal structures (monazite vs. zircon) and chemical compositions (phosphates vs. silicates) for these phases. Pure synthetic single crystals of ZrSiO4, monoclinic ThSiO4, LaPO4 and ScPO4 were irradiated...
In this research, the specific fracture energy of almandine, zircon and periclase (MgO) are presented. The materials measured were in powder form during the measurement. A method of crushing the materials using a hydraulic press was used, followed by statistical analysis of the change in the surface of the powder. Values were taken from particle si...
The world-class Sn-Nb-Ta Madeira deposit is located in the Pitinga mine (northern Brazil). The deposit is associated with the albite-enriched granite facies of the A-type Madeira Granite (∼1820 Ma). The mine commercially extracts tin (cassiterite), Nb and Ta (U-Pb-pyrochlore and columbite). Fluorine (cryolite), Y, REE (xenotime), Zr (zircon), U (U-...
The beneficiations of a complex rare earth element (REE) ore containing REE minerals of carbonates, silicates and oxides and other REE bearing minerals (e.g. zircon and pyrochlore etc.) by flotation and high gradient magnetic separation (HGMS) were investigated. The recoveries of the different group of minerals in the flotation concentrates and the...
Citations
... As shown in the XRD result [ Fig. 6(a)], the HfO 2 film obtained using HfCp(edpa) 3 has a mixed plane (monoclinic and cubic/tetragonal), and thus, it is estimated that the dielectric constant is between the values for HfO 2 in the monoclinic phase (14)(15)(16) 49,50 and the cubic/tetragonal phase (28)(29)(30). 51,52 The interface trap density (D it ) calculated using the conductance method was 8.63 × 10 11 eV −1 cm −2 . 5 The trapped oxide charge (Not) obtained using the mid-gap charge separation method was −2.71 × 10 11 cm −2 for HfO 2 produced using HfCp(edpa) 3 . ...
Alkoxide precursors have been highlighted for depositing carbon-free films, but their use in Atomic Layer Deposition (ALD) often exhibits a non-saturated growth. This indicates no self-limiting growth due to the chain reaction of hydrolysis or ligand decomposition caused by β-hydride elimination. In the previous study, we demonstrated that self-limiting growth of ALD can be achieved using our newly developed precursor, hafnium cyclopentadienyl tris(N-ethoxy-2,2-dimethyl propanamido) [HfCp(edpa)3]. To elucidate the growth mechanism and the role of cyclopentadienyl (Cp) ligand in a heteroleptic alkoxide precursor, herein, we compare homoleptic and heteroleptic Hf precursors consisting of N-ethoxy-2,2-dimethyl propanamido (edpa) ligands with and without cyclopentadienyl ligand—hafnium tetrakis(N-ethoxy-2,2-dimethyl propanamido) [Hf(edpa)4] and HfCp(edpa)3. We also investigate the role of a Cp ligand in growth characteristics. By substituting an alkoxide ligand with a Cp ligand, we could modify the surface reaction during ALD, preventing undesired reactions. The last remaining edpa after Hf(edpa)4 adsorption can undergo a hydride elimination reaction, resulting in surface O–H generation. In contrast, Cp remains after the HfCp(edpa)3 adsorption. Accordingly, we observe proper ALD growth with self-limiting properties. Thus, a comparative study of different ligands of the precursors can provide critical clues to the design of alkoxide precursors for obtaining typical ALD growth with a saturation behavior.
... The electron transfer to the surface of adsorbates is reliant on both the redox potential and the location of band edges, which must be adequate for the process to occur effectively [44]. The band edge's locations of the samples were estimated by Mulliken electronegativity and the value of band gap of AlAuO 2 using B3LYP method, which are shows using the following equations [7,8,45]. ...
In this study, density functional theory (DFT) simulations have been used to study the structural, electrical and optical properties of AlAuO 2 and AlAu 094 Fe 006 O 2. Initially, the estimated bandgap of AlAuO 2 0.45, 0.486, 0.419 and 2.49 eV in Perdew-Burke-Ernzerhof (PBE), Revised Perdew-Burke-Ernzerhof (RPBE), PBE for solids (PBE sol) and Becke three-parameter Lee-Yang-Parr (B3LYP) method respectively while AlAu 094 Fe 006 O 2 has a zero-band gap after 6 % Fe doping. Then, density of state (DOS) and partial density of state (PDOS) were studied to determine the characteristics of the various orbitals of AlAuO 2. The bonding characteristics and thermal stability of this crystal are determined by the Mulliken population charge and thermos physical parameters. Band edge of AlAuO 2 was calculated which revealed that the AlAuO 2 has suitable oxidation and reduction potential to degrade the contamination. A remarkable absorption has recorded for both AlAuO 2 and AlAu 094 Fe 006 O 2 in visible and ultraviolet region and capability to utilize pho-tocatalytic dye degradation and hydrogen production through water splitting.
... These oxide compounds can be formed from alkaline metals, transition metals, and other metals [1,2]. Transition metal oxides (TMOs) are very attractive due to their complex electronic structure and different oxidation states, which make them suitable for dielectric [3], electrochromic [4], capacitive [5], and semiconducting properties [6]. As semiconductors, TMOs have allowed the development of several types of devices used in applications such as solar cells, diodes, light emission diodes (LEDs), photodetectors, and transistors involving n-type and p-type semiconductors. ...
Thermally processed nickel oxide (NiO) thin films were synthesized from nickel hydroxide films obtained by chemical solution deposition. Potential applications derived from electronic properties were studied by thermally treated thin films under two controlled annealing atmospheres. The NiO thin films with thicknesses between 160 and 192 nm and a nanowall-like morphology were obtained. Amorphous thin films with high optical transmittance in the visible region of around 85 % and ∼3.7 eV bandgap energy were obtained. The chemical composition of the NiO films was determined by X-ray photoelectron spectroscopy (XPS), which confirmed that the films were indeed composed of NiO after thermal treatment. The electrical properties were acquired through the Hall effect technique. The NiO films exhibit a p-type conductivity; the highest carrier concentration is 5×1015 cm−3. Mobility up to 11 cm2∙V−1∙S−1 and low resistivity of 9×102 Ω∙cm. These properties are suitable for applications in transparent electronic devices.
... Another effect of a reduced size and stress is the possible stabilization of metastable phases, an effect that is used, for example, for the stabilization of high-symmetry phases in polycrystalline HfO 2 films for boosting the dielectric permittivity or inducing ferroelectricity. 8,9 Polycrystalline HfO 2 -based ferroelectric thin films are typically highly heterogeneous materials with a mixture of the ferroelectric orthorhombic Pca2 1 phase together with nonferroelectric monoclinic or tetragonal phases and with grain sizes of 5−20 nm. 10−12 Advanced transmission electron microscopy (TEM) methods are key in evidencing the crystalline phases in thin heterogeneous films and the curled polar textures. ...
Reducing the dimensions of ferroelectric materials down to the nanoscale has strong implications on the ferroelectric polarization pattern and on the ability to switch the polarization. As the size of ferroelectric domains shrinks to the nanometer scale, the heterogeneity of the polarization pattern becomes increasingly pronounced, enabling a large variety of possible polar textures in nanocrystalline and nanocomposite materials. Critical to the understanding of fundamental physics of such materials and hence their applications in electronic nanodevices is the ability to investigate their ferroelectric polarization at the nanoscale in a nondestructive way. We show that contact Kelvin probe force microscopy (cKPFM) combined with a k-means response clustering algorithm enables to measure the ferroelectric response at a mapping resolution of 8 nm. In a BaTiO3 thin film on silicon composed of tetragonal and hexagonal nanocrystals, we determine a nanoscale lateral distribution of discrete ferroelectric response clusters, fully consistent with the nanostructure determined by transmission electron microscopy. Moreover, we apply this data clustering method to the cKPFM responses measured at different temperatures, which allows us to follow the corresponding change in the polarization pattern as the Curie temperature is approached and across the phase transition. This work opens up perspectives for mapping complex ferroelectric polarization textures such as curled/swirled polar textures that can be stabilized in epitaxial heterostructures and more generally for mapping the polar domain distribution of any spatially highly heterogeneous ferroelectric materials.
... 43 Amorphous HfO 2 (ϵ r 20 À 25) is another example of an enhanced permittivity compared to the monoclinic phase (ϵ r 16), which is the stable phase at room temperature and atmospheric pressure, while higher symmetry phases (such as cubic, tetragonal, or orthorhombic) have larger permittivities. [44][45][46] The enhanced permittivity in our GaO x films compared to the one of The leakage current density as a function of applied voltage is shown in Fig. 6(a) for 30 nm films prepared with different O 2 plasma exposure times. For positive voltages, the diodelike behavior observed for 3 and 8 s exposure is attributed to the p-n junction formed between GaO x and silicon. ...
Amorphous gallium oxide thin films were grown by plasma-enhanced atomic layer deposition on (100) silicon substrates from trimethylgalliumGa(CH3)3precursor and oxygen plasma. At 200 °C, the growth per cycle is in the range of 0.65–0.70 Å for O2plasma exposure times rangingfrom 3 up to 30 s during each cycle. The effect of O2plasma exposure times on the interfacial SiOxregrowth and the electrical properties wasinvestigated.In situspectroscopic ellipsometry shows that the SiOxregrowth occurs during the first three cycles and is limited to 0.27 nm forplasma times as long as 30 s. Increasing the O2plasma exposure during each ALD cycle leads to a drastic decrease in the leakage currentdensity (more than 5 orders of magnitude for 30 nm films), which is linked to the suppression of oxygen vacancy states as evidenced by spec-troscopic ellipsometry. Interestingly, an increase in the dielectric constant with increasing O2plasma exposure time is observed, reaching avalue ofεr�14:2, larger than that of single crystallineβ-Ga2O3. This study highlights the crucial role of oxygen plasma exposure time in thecontrol and tuning of the electrical properties of amorphous gallium oxide films.
... These materials can be applied in oxygen sensors and fuel cells systems Particularly, ZrO 2 has been used in the thermal coating in jet engines and gas turbines [1]. Both systems can exist in different polymorphs depending on the different growth circumstances [2]. The most stable crystal structure of the systems is the monoclinic structure (space group: P2 1 /c) which typically forms after the annealing treatment on the asdeposited amorphous films [3,4]. ...
... A saturation of n eff is achieved at threshold energy at which ε 2 is zero and no longer induces the increase of n eff based on equation (6). Additionally, the zero ε 2 corresponds to zero k based on equation (2). ZrO 2 and HfO 2 systems show that n eff reaches saturation at threshold energy of ∼10.4 and ∼10.0 eV, respectively. ...
We study structural, electronic, and optical properties of the monoclinic Hf0.5Zr0.5O2 (space group: P21/c). Monoclinic ZrO2 and HfO2 systems are used as the references. This study employs the plane-wave density-functional method within the generalized gradient approximation. The structural properties emphasize the strongest local-symmetry distortion in Hf0.5Zr0.5O2 system. The bandgap (3.67 eV) and valence bandwidth (~4.94 eV) of the system are between that of ZrO2 and HfO2 systems. Furthermore, the negative average defect formation energy confirms the stability of Hf0.5Z0.5O2 system. In all the systems, the significant differences between n0x(n0y) and n0z imply the strong optical dichroism between xy plane and z axis. On the other hand, the small differences between n0x and n0y imply the weak optical dichroism along xy plane. In Hf0.5Zr0.5O2 system, the optical properties show the zero-frequency refractive indices of (n0x, n0y, n0z) = (2.039, 2.086, 1.851). The system also shows the highest intensity and weakest dichroism of plasmonic states along y axis and xy plane, respectively. Moreover, we find the lowest energy level of maximum transmittance (T ≈ 1), strong-reflectance width, absorption width, and saturation threshold energy (~9.6 eV) of the effective number of valence electrons. Our result emphasizes the importance of the doping treatment to the significant tuning of optical properties of Hf1-xZrxO2 system. This study presents the essential properties to guide future experiments to develop novel optical devices.
... Ab initio calculations suggest that high symmetry phases of HfO 2 viz. cubic, tetragonal and orthorhombic have a higher dielectric constant (κ>25) than the monoclinic phase (κ~16-20) [3, 4]. It is therefore desirable to stabilize a higher symmetry phase of HfO 2 which in fact, also turns out to be a challenge as it only stabilizes at very high temperatures i.e. 2700 ̊ C for the bulk cubic polymorph. ...
Hafnia is one of the most widely used wide gap materials in the microelectronic industry. Stemming from the need to miniaturize electronic devices, high κ materials such as hafnia-based compounds replace SiO2 in gate oxides, thereby decreasing the equivalent oxide thickness of the gate dielectric. On the other hand, scaling down deteriorates the physical
properties of the latter viz., leakage current and carrier mobility. By increasing κ or the electric constant of the material, these losses can nevertheless be compensated for. Doping of HfO2 is known to increase its κ; these dopants include mostly divalent elements such as Mg or trivalent elements such as Y, Al and La. Multivalent elements such as V and Ta are also used as dopants but their oxidation state depends upon the growth conditions. Doping via elements with +2 and +3 oxidation states, has a propensity to introduce oxygen vacancies and stabilize higher symmetry phases of HfO2 i.e. cubic, tetragonal and even orthorhombic which present higher κ compared to the monoclinic phase. In all cases, the electronic structure of the material at the atomic level, varies as a function of crystallinity, crystal structure, oxygen vacancies and dopants; all of which affect bond lengths and in turn the atomic bonding and thereby the hybridization. Moreover, the electronic properties also affect the physical properties of the gate oxide and therefore, understanding the xidation state of the dopants which affect the electronic structure of HfO2 by probing the O-K edge Energy Loss Near Edge Structure (ELNES) of the material via Electron Energy Loss Spectroscopy (EELS) in the Scanning/Transmission Electron Microscope (STEM), is indispensable. In fact, by using techniques such as Spectral Imaging (SI) and Energy Filtered Transmission Electron Microscopy (EFTEM), it is now tractable to study the diffusion of dopants within HfO2. When EFTEM is coupled with (ELNES), local changes in the electronic structure as a function of the concentration of dopants are revealed.
... In this expression, α M is the Madelung constant for the supercell, calculated using the method described in Ref. 28. is the static dielectric constant; it has been obtained from a phonon calculation in the unit cell of ZnIr 2 O 4 assuming an average value of 6.0 for the high-frequency part of the dielectric constant, which is a good approximation for most oxides. 29 We obtain a value of 9.38 with the B3LYP functional. L is the average distance between defect images and f is a proportionality factor accounting for the L −3 term, which is −0.35 according to Lany and Zunger. ...
We analyze by means of ab initio calculations the role of imperfections on the electronic structure of ZnIr2O4, ranging from point defects in the spinel phase to the fully amorphous phase. We find that interstitial defects and anion vacancies in the spinel have large formation energies, in agreement with the trends observed in other spinels. In contrast, cation vacancies and antisites have lower formation energies. Among them, the zinc antisite and the zinc vacancy are the defects with the lowest formation energy. They are found to act as acceptors, and may be responsible for the spontaneous hole doping in the material. They may also induce optical transitions that would reduce the transparency of the material. Amorphization of ZnIr2O4 leads a large decrease of the band gap and appearance of localized states at the edges of the band gap region, which may act as charge traps and prevent amorphous ZnIr2O4 from being a good hole conductor.
... similar to that reported for tetragonal-phase HfO 2 . 22 The dielectric film thicknesses estimated from these measurements are 3, 8.4, and 12.9 nm, which are slightly higher than the target values and those calculated from the MEIS. accumulation region at low frequencies can be explained by the increase in the oxide leakage current after FGA. ...
This paper describes the deposition and characterization of Ce-modified HfO2 thin films. Layers were deposited on Si(100) substrates by thermal atomic layer deposition using (MeCp)2Hf(OMe)(Me), Ce(mmp)4, and H2O as the precursors. Spectroscopic ellipsometry and medium energy ion scattering were used to measure the thicknesses and compositions of the deposited films. After postdeposition annealing, a metastable cubic phase is found to be stabilized in the films. Capacitance–voltage measurements have been used to characterize the dielectric properties of deposited films before and after two annealing regimes. The equivalent oxide thickness of an as-deposited sample with nominal high-κ dielectric thickness of 6 nm is circa 2.8 nm from which the dielectric constant 31 was calculated. The leakage current density is in order of 10−6 A/cm2 at ±1 V. The fabrication of Ce-HfO2 films without plasma or O3-based atomic layer deposition represents a potentially useful manufacturing route for future scaled devices.
... 2 For MIM devices, ZrO 2 is preferred for its capacitance density and leakage current, 3 strongly influenced by intrinsic properties such as crystallinity and interface quality. 4 The permittivity of such dielectric depends on its crystalline structure, reaching the value of 47 in the tetragonal phase. 5 In addition, ZrO 2 presents a large bandgap (around 5.5 eV). ...
In this paper, we report the growth of ZrO2 thin films on TiN substrates using Plasma Enhanced Atomic Layer Deposition (PEALD) process starting from cyclopentadienyltris(dimetylamino)zirconium and oxygen plasma as precursor and reactant, respectively. The material properties - structure, morphology and composition - are investigated as a function of process parameters such as number of cycles, deposition temperature and plasma conditions. Electrical performances - in terms of breakdown field and leakage currents - are investigated as a function of deposition temperature on Au/ZrO2/TiN capacitors, giving an evidence for an impact of the crystallinity and impurities. (C) 2014 The Electrochemical Society.
