Surface immobilization of Mo6I8 octahedral cluster cores on functionalized amorphous carbon using a pyridine complexation strategy

Tetrahedral amorphous carbon (a-C) films have been grown by pulsed laser deposition to investigate a liquid phase process for surface immobilization of electroactive [Mo₆Iⁱ₈]^4 + transition metal cluster cores using a complexation reaction with a pyridine-terminated alkyl monolayer covalently bonded to the a-C surface (Py^S–alkyl/a-C). These films are stable against thermally-assisted grafting of alkene molecules and the covalent CC interface provides a robust monolayer/a-C assembly. Octahedral [Mo₆Iⁱ₈]^4 + cluster cores with iodine inner ligands and labile triflate apical ligands [Mo₆Iⁱ₈(CF₃SO₃)^a₆]^2 − have been immobilized through partial complexation in apical positions by surface pyridine groups (Py^S). The remaining CF₃SO₃⁻ apical ligands of [Mo₆Iⁱ₈ (Py^S)^a_y(CF₃SO₃)^a_6 − y] cluster units were further substituted with bromopyridine (Py-Br) to obtain air stable surface with expected final composition [Mo₆Iⁱ₈ (Py^S)^a_y(Py-Br)^a_6 − y]. The yield of the different reaction steps is followed by X-ray photoelectron spectroscopy, providing cluster coverage Σ_Mo6I8 = 9 × 10¹² cm^− 2. Each [Mo₆I₈]^4 + cluster is bound to the carbon surface through multiple anchoring metal sites (N_PYR = 3 or 4), indicating that pyridine-terminated alkyl chains are flexible enough to accommodate four bonds. Electrical transport through Hg//Mo₆I₈–Py^S–alkyl/a-C/p-Si(111) junctions shows rectifying current–voltage characteristics but does not reveal any signature of cluster immobilization.     

Aqueous dispersion of 1D van der Waals Mo6S3I6 crystal using biocompatible tri-block copolymer

To achieve the stable dispersion of 1D van der Waals crystal Mo₆S₃I₆ in aqueous media, the tri-block copolymer (Poloxamer) is used as dispersant. The head group of Poloxamer, hydrophobic polypropylene oxide parts can be adsorbed to Mo₆S₃I₆ surface by hydrophobic interaction and the tail group with hydrophilic polyethylene oxide exposed to the outside of the Mo₆S₃I₆ is soluble in water and can form sufficient steric hindrance, resulting in stable aqueous dispersion in nm scale. The excellent biocompatibility of aqueous dispersed nm scale 1D Mo₆S₃I₆ was demonstrated by effective proliferation of C2C12 cells.     

Resistive switching memory characteristics of Ge/GeOx nanowires and evidence of oxygen ion migration

The resistive switching memory of Ge nanowires (NWs) in an IrO_x/Al₂O₃/Ge NWs/SiO₂/p-Si structure is investigated. Ge NWs with an average diameter of approximately 100 nm are grown by the vapor–liquid-solid technique. The core-shell structure of the Ge/GeO_x NWs is confirmed by both scanning electron microscopy and high-resolution transmission electron microscopy. Defects in the Ge/GeO_x NWs are observed by X-ray photoelectron spectroscopy. Broad photoluminescence spectra from 10 to 300 K are observed because of defects in the Ge/GeO_x NWs, which are also useful for nanoscale resistive switching memory. The resistive switching mechanism in an IrO_x/GeO_x/W structure involves migration of oxygen ions under external bias, which is also confirmed by real-time observation of the surface of the device. The porous IrO_x top electrode readily allows the evolved O₂ gas to escape from the device. The annealed device has a low operating voltage (<4 V), low RESET current (approximately 22 μA), large resistance ratio (>10³), long pulse read endurance of >10⁵ cycles, and good data retention of >10⁴ s. Its performance is better than that of the as-deposited device because the GeO_x film in the annealed device contains more oxygen vacancies. Under SET operation, Ge/GeO_x nanofilaments (or NWs) form in the GeO_x film. The diameter of the conducting nanofilament is approximately 40 nm, which is calculated using a new method.     

Large-scale and uniform preparation of pure-phase wurtzite GaAs NWs on non-crystalline substrates

One of the challenges to prepare high-performance and uniform III-V semiconductor nanowires (NWs) is to control the crystal structure in large-scale. A mixed crystal phase is usually observed due to the small surface energy difference between the cubic zincblende (ZB) and hexagonal wurtzite (WZ) structures, especially on non-crystalline substrates. Here, utilizing Au film as thin as 0.1 nm as the catalyst, we successfully demonstrate the large-scale synthesis of pure-phase WZ GaAs NWs on amorphous SiO₂/Si substrates. The obtained NWs are smooth, uniform with a high aspect ratio, and have a narrow diameter distribution of 9.5 ± 1.4 nm. The WZ structure is verified by crystallographic investigations, and the corresponding electronic bandgap is also determined to be approximately 1.62 eV by the reflectance measurement. The formation mechanism of WZ NWs is mainly attributed to the ultra-small NW diameter and the very narrow diameter distribution associated, where the WZ phase is more thermodynamically stable compared to the ZB structure. After configured as NW field-effect-transistors, a high I_ON/I_OFF ratio of 10⁴ − 10⁵ is obtained, operating in the enhancement device mode. The preparation technology and good uniform performance here have illustrated a great promise for the large-scale synthesis of pure phase NWs for electronic and optical applications.     

Sonochemical synthesis of mesoporous GdxZryTizCe1−x–y–zO2 solid solution

Gd_xZr_yTi_zCe_{1−x–y–z}O₂ (x+y+z≤0.3) solid solutions with a crystallite size of 5–10 nm have been prepared by the sonochemical method from inorganic salts without any additives. In all cases, ceria based materials exhibited a mesoporous structure with polymodal pore size distribution with diameter of 2–10 nm. It was shown that crystallite size and specific surface area remained practically unchanged while changing the dopant concentration.     

Intrinsic defects,Mo-related defects,and complexes in transition-metal carbide VC: A first-principles study

Intrinsic defects and Mo-related defects in vanadium carbide VC, as well as the defect complexes between vacancies and Mo defects were investigated by means of first-principles calculations within the framework of density functional theory. In addition, Mo diffusion in VC was also studied using LST/QST method. The formation energies of defects have clearly shown that except C vacancy (V_C) all other point defects are not energetic favorable compared to perfect VC. V_C can exist in the lattice forming nonstoichiometric carbide VC_x (x < 1), and also can stabilize the Mo-related defects (S_Mo-V, S_Mo-C, and T_Mo). Free Mo atoms have the strong tendency to enter the already formed V_V and occupy the lattice position of V atoms. Meanwhile, Mo atom in C lattice (S_Mo-C) and interstitial Mo (I_Mo) atom can also enter the V_V position stabilizing the lattice structure. S_Mo-C + V_V will transform into S_Mo-V + V_C and I_Mo + V_V will transform into S_Mo-V during optimization, and large binding energy makes Mo atom tend to exist in the interstitial position. From the perspective of energy, Mo atom tends to diffuse through the interstitial position.     

Kinetics and PEMFC performance of RuxMoySez nanoparticles as a cathode catalyst

Kinetics of Ru_xMo_ySe_z nanoparticles dispersed on carbon powder was studied in 0.5 M H₂SO₄ electrolyte towards the oxygen reduction reaction (ORR) and as cathode catalysts for a proton exchange membrane fuel cell (PEMFC). Ru_xMo_ySe_z catalyst was synthesized by decarbonylation of transition-metal carbonyl compounds for 3 h in organic solvent. The powder was characterized by X-ray diffraction (XRD), and transmission electron microscopy (TEM) techniques. Catalyst is composed of uniform agglomerates of nanocrystalline particles with an estimated composition of Ru₆Mo₁Se₃, embedded in an amorphous phase. The electrochemical activity was studied by rotating disk electrode (RDE) and rotating ring-disk electrode (RRDE) techniques. Tafel slopes for the ORR remain invariant with temperature at −0.116 V dec⁻¹ with an increase of the charge transfer coefficient in dα/dT = 1.6 × 10⁻³, attributed to an entropy turnover contribution to the electrocatalytic reaction. The effect of temperature on the ORR kinetics was analyzed resulting in an apparent activation energy of 45.6 ± 0.5 kJ mol⁻¹. The catalyst generates less than 2.5% hydrogen peroxide during oxygen reduction. The Ru_xMo_ySe_z nanoparticles dispersed on a carbon powder were tested as cathode electrocatalyst in a single fuel cell. The membrane-electrode assembly (MEA), included Nafion^® 112 as polymer electrolyte membrane and commercial carbon supported Pt (10 wt%Pt/C-Etek) as anode catalyst. It was found that the maximum performance achieved for the electro-reduction of oxygen was with a loading of 1.0 mg cm⁻² Ru_xMo_ySe_z 20 wt%/C, arriving to a power density of 240 mW cm⁻² at 0.3 V and 80 °C.     

Zn3N2 nanowires: growth,properties and oxidation

Zinc nitride (Zn₃N₂) nanowires (NWs) with diameters of 50 to 100 nm and a cubic crystal structure have been grown on 1 nm Au/Al₂O₃ via the reaction of Zn with NH₃ including H₂ between 500°C and 600°C. These exhibited an optical band gap of ≈ 3.2 eV, estimated from steady state absorption-transmission spectroscopy. We compared this with the case of ZnO NWs and discussed the surface oxidation of Zn₃N₂ NWs which is important and is expected to lead to the formation of a Zn₃N₂/ZnO core-shell NW, the energy band diagram of which was calculated via the self-consistent solution of the Poisson-Schrödinger equations within the effective mass approximation by taking into account a fundamental energy band gap of 1.2 eV. In contrast, only highly oriented Zn₃N₂ layers with a cubic crystal structure and an optical band gap of ≈ 2.9 eV were obtained on Au/Si(001) using the same growth conditions.     

Single‐Crystalline Mesoporous Molybdenum Nitride Nanowires with Improved Electrochemical Properties

We report single‐crystalline mesoporous molybdenum nitride nanowires (meso‐Mo₃N₂‐NWs) prepared by topotactic reaction using single‐crystalline molybdenum oxide nanowires. The single‐crystalline nature of meso‐Mo₃N₂‐NWs was clearly observed by field‐emission transmission electron microscopy. The meso‐Mo₃N₂‐NWs exhibited mesoporous structure with ～45 m²/g in specific surface area and ～4.6 nm in average pore size confirmed by a nitrogen sorption measurement. Due to high specific surface area and mesoporous structure, meso‐Mo₃N₂‐NWs showed much higher specific capacitance and excellent charging–discharging performance as compared with Mo₃N₂ prepared using conventional nitridation process.     

Stabilization and superconductivity of AlB2-type nonstoichiometric molybdenum diboride by Sc doping

Molybdenum diboride is unique among transition metal diborides because it exists in both hexagonal (AlB₂-type) and rhombohedral structures. However, it is difficult to stabilize the superconducting AlB₂-type phase, which requires either extreme synthesis condition or suitable chemical doping. Here we report the structural and physical properties of Sc-doped nonstoichiometric molybdenum diborides (Mo_0.95Sc_0.05)_1-xB₂ and (Mo_1-ySc_y)_0.71B₂ prepared by the common arc melting method. The AlB₂-type phase is found to form over wide ranges of 0 ≤ x ≤ 0.29 and 0.025 ≤ y ≤ 0.30 for the first time, and bulk superconductivity with T_c up to 7.9 K is observed. T_c increases with increasing x in the (Mo_0.95Sc_0.05)_1-xB₂ series, but evolves nonmonotonically with varying y in the (Mo_1-ySc_y)_0.71B₂ series. Despite this contrast, T_c of both borides follows nearly the same linear dependence on the electron-phonon coupling constant, suggesting that it is mainly controlled by the electron-phonon interaction. In addition, the stabilization of AlB₂-type structure is attributed to the decrease in the number of d electrons as a consequence of Sc doping, which suggests that a similar effect may be achieved by substituting Mo with other d electron-poorer metal elements.     

Mo doping-enhanced dye absorption of Bi2Se3 nanoflowers

A simple solvothermal approach is explored to prepare Bi_2−xMo_xSe₃ nanostructures by employing N,N-dimethylformamide (DMF) as the solvent. Mo plays an important role in the assembly of the Bi_2−xMo_xSe₃ nanostructures from nanoplates to nanoflowers. Structural and morphological studies indicate that the resulting products are large specific surface area single-crystalline Bi_2−xMo_xSe₃ nanoflowers self-assembled from thin nanoplates during the reaction process. The absorption properties of the as-prepared samples are investigated with Rhodamine B (RhB) as dye, and it is found that the Bi_1.85Mo_0.15Se₃ nanoflowers show an optimal adsorption capacity, implying that Mo doping not only changes the morphologies of the nanostructures but also enhances their absorption behaviors.     

Tunable structure and intensive upconversion photoluminescence for Ho3+-Yb3+ codoped bismuth titanate composite synthesized by sol-gel-combustion (SGC) method

Ho³⁺ and Yb³⁺ codoped bismuth titanate (BTO) composite powders with infrared to visible upconversion luminescence (UCL) function were prepared by SGC method. The effects of Ho³⁺ and Yb³⁺ doping content on the structure and property were investigated for BTO: xHo, 0.2 Yb (x = 0, 0.02, 0.04, 0.06, 0.08, 0.1) and BTO: 0.02Ho, yYb (y = 0.1, 0.2, 0.3, 0.5, 0.7, 0.9) samples. All the samples include three bismuth titanate phases (Bi₄Ti₃O₁₂, Bi₂Ti₂O₇, and Bi₂₀TiO₃₂), and the phase proportion can be tuned by changing Ho³⁺ and Yb³⁺ doping content. These powders are well crystalized with honeycomb-like microscopic structure, and with good absorption for 233 nm, 310 nm and 975 nm wavelength. The band gap can be tuned from 3.53 eV to 4.03 eV when increasing Yb³⁺ content from y = 0 to y = 0.9. A strong 530–580 nm green emission band and a relative weak 630–690 nm red one corresponding to Ho³⁺: ⁵S₂ → ⁵I₈ and ⁵F₅ → ⁵I₈ transitions appear in the UCL spectra for all the BTO: Ho, Yb samples when pumped at 980 nm. The emission intensities can well be tuned with various Ho³⁺ and Yb³⁺ content. The optimal UCL was obtained in BTO: 0.02Ho, 0.5 Yb for all the prepared samples. The energy transfer mechanism is analyzed by building a two-photon energy transfer model, which is proved by the relationship between emission intensities and pumping power measurement. The concentration quenching of Ho³⁺ is caused by cross relaxation of CR₁ and CR₂ (Ho: ⁵F₄, ⁵S₂ + ⁵I₈ → ⁵I₄ + ⁵I₇) and by CR₃ (Ho: ⁵F₄, ⁵S₂ + Yb: ²F_7/2 → Ho: ⁵I₆ + Yb: ²F_5/2) for Yb³⁺ quenching. The mean luminescence lifetime (τ_m) from Ho: ⁵S₂ decreases monotonously with the increase of Ho³⁺ and Yb³⁺ content.     

Effect of chalcogen substitution in mixed Mo6S8−nSen (n = 0, 1, 2) Chevrel phases on the thermodynamics and kinetics of reversible Mg ions insertion

The effect of the partial substitution of S by Se atoms in the Mo₆Se_8−nS_n Chevrel phases (CPs), (n = 0, 1, 2), on the reversible intercalation of Mg ions into these hosts was studied by a combination of cyclic voltammetry (CV), galvanostatic cycling, potentiostatic intermittent titration (PITT) and electrochemical impedance spectroscopy (EIS) techniques. Based on the previously published structural characterizations of the CP compounds under study, we describe herein the thermodynamic effect of the substitution in terms of the transformation of a single peak of the differential capacitance for the pure Mo₆X₈ phases (X = S or Se), into a set of a lower amplitude and broader peaks for the mixed (S, Se) CPs, located at less positive potentials compared to that for the pure CP. This is due to the preferential ordering of the Se anions (as compared to that of S anions) in their sites in the CP's crystal structure. In addition to the thermodynamic effect of the substitution, the geometry of the transition state for the mobile Mg ions is modified, thus facilitating the insertion of Mg ions into the partially substituted CP compounds (the kinetic effect). Thereby, the partial charge trapping that characterizes Mg ion insertion into sulfide-based CPs at low temperatures vanishes in the Mg_xMo₆S₆Se₂ compounds. This was nicely confirmed by impedance (EIS) measurements in combination with chronopotentiometry.     

Tuning of structural,optical, and magnetic properties of ultrathin and thin ZnO nanowire arrays for nano device applications

One-dimensional (1-D) ultrathin (15 nm) and thin (100 nm) aligned 1-D (0001) and (0001¯) oriented zinc oxide (ZnO) nanowire (NW) arrays were fabricated on copper substrates by one-step electrochemical deposition inside the pores of polycarbonate membranes. The aspect ratio dependence of the compressive stress because of the lattice mismatch between NW array/substrate interface and crystallite size variations is investigated. X-ray diffraction results show that the polycrystalline ZnO NWs have a wurtzite structure with a = 3.24 Å, c = 5.20 Å, and [002] elongation. HRTEM and SAED pattern confirmed the polycrystalline nature of ultrathin ZnO NWs and lattice spacing of 0.58 nm. The crystallite size and compressive stress in as-grown 15- and 100-nm wires are 12.8 nm and 0.2248 GPa and 22.8 nm and 0.1359 GPa, which changed to 16.1 nm and 1.0307 GPa and 47.5 nm and 1.1677 GPa after annealing at 873 K in ultrahigh vacuum (UHV), respectively. Micro-Raman spectroscopy showed that the increase in E₂ (high) phonon frequency corresponds to much higher compressive stresses in ultrathin NW arrays. The minimum-maximum magnetization magnitude for the as-grown ultrathin and thin NW arrays are approximately 8.45 × 10⁻³ to 8.10 × 10⁻³ emu/g and approximately 2.22 × 10⁻⁷ to 2.190 × 10⁻⁷ emu/g, respectively. The magnetization in 15-nm NW arrays is about 4 orders of magnitude higher than that in the 100 nm arrays but can be reduced greatly by the UHV annealing. The origin of ultrathin and thin NW array ferromagnetism may be the exchange interactions between localized electron spin moments resulting from oxygen vacancies at the surfaces of ZnO NWs. The n-type conductivity of 15-nm NW array is higher by about a factor of 2 compared to that of the 100-nm ZnO NWs, and both can be greatly enhanced by UHV annealing. The ability to tune the stresses and the structural and relative occupancies of ZnO NWs in a wide range by annealing has important implications for the design of advanced photonic, electronic, and magneto-optic nano devices.     

The nitridation of ZnO nanowires

ZnO nanowires (NWs) with diameters of 50 to 250 nm and lengths of several micrometres have been grown by reactive vapour transport via the reaction of Zn with oxygen on 1 nm Au/Si(001) at 550°C under an inert flow of Ar. These exhibited clear peaks in the X-ray diffraction corresponding to the hexagonal wurtzite crystal structure of ZnO and a photoluminescence spectrum with a peak at 3.3 eV corresponding to band edge emission close to 3.2 eV determined from the abrupt onset in the absorption-transmission through ZnO NWs grown on 0.5 nm Au/quartz. We find that the post growth nitridation of ZnO NWs under a steady flow of NH₃ at temperatures ≤600°C promotes the formation of a ZnO/Zn₃N₂ core-shell structure as suggested by the suppression of the peaks related to ZnO and the emergence of new ones corresponding to the cubic crystal structure of Zn₃N₂ while maintaining their integrity. Higher temperatures lead to the complete elimination of the ZnO NWs. We discuss the effect of nitridation time, flow of NH₃, ramp rate and hydrogen on the conversion and propose a mechanism for the nitridation.     

Kinetic study of H-terminated silicon nanowires oxidation in very first stages

Oxidation of silicon nanowires (Si NWs) is an undesirable phenomenon that has a detrimental effect on their electronic properties. To prevent oxidation of Si NWs, a deeper understanding of the oxidation reaction kinetics is necessary. In the current work, we study the oxidation kinetics of hydrogen-terminated Si NWs (H-Si NWs) as the starting surfaces for molecular functionalization of Si surfaces. H-Si NWs of 85-nm average diameter were annealed at various temperatures from 50°C to 400°C, in short-time spans ranging from 5 to 60 min. At high temperatures (T ≥ 200°C), oxidation was found to be dominated by the oxide growth site formation (made up of silicon suboxides) and subsequent silicon oxide self-limitation. Si-Si backbond oxidation and Si-H surface bond propagation dominated the process at lower temperatures (T < 200°C).     

Preparation of Mo2C by the temperature-programmed reaction between h-MoO3 and CO

In the work, the temperature-programmed reaction (TPR) between hexagonal-shaped h-MoO₃ and high-purity CO under different heating rates was investigated in order to prepare Mo₂C. Various technologies such as TG-DTA-DTG, XRD, FESEM, FT-IR and Raman spectrum as well as the thermodynamic calculation were adopted to analyze the experimental data. The results showed that the physically adsorbed water on the sample surface, the residual ammonium and coordinated water in the internal structure of h-MoO₃ were successively released as the temperature increased, and then α-MoO₃ and Mo₄O₁₁ were formed when the temperature arrived at around 791 K. Upon further increasing the temperature, the reduction process occurred and MoO₂ will be generated. Thereafter, the carburization reaction was taken place and the subsequent reaction pathways were significantly different at lower and higher heating rates: at lower heating rates (8 and 12 K/min), the carburization process of MoO₂ to Mo₂C followed MoO₂→MoO₂+Mo₂C→Mo₂C + Mo→Mo₂C; while at higher heating rates (16 and 20 K/min), the reaction pathways followed MoO₂→MoO₂+Mo₂C→MoO₂+Mo₂C + Mo + MoO_xC_y→Mo→Mo₂C, single-phase metallic Mo can be generated. The work also discovered that the as-prepared Mo₂C always kept the same platelet-shaped morphology as that of the newly-formed MoO₂; while due to the removal of oxygen and the decrease of molar volume during the transformation process, the as-prepared Mo₂C exhibited a rougher and more porous morphological structure.     

The MoS2 Nanotubes with Defect-Controlled Electric Properties

We describe a two-step synthesis of pure multiwall MoS₂ nanotubes with a high degree of homogeneity in size. The Mo₆S₄I₆ nanowires grown directly from elements under temperature gradient conditions in hedgehog-like assemblies were used as precursor material. Transformation in argon-H₂S/H₂ mixture leads to the MoS₂ nanotubes still grouped in hedgehog-like morphology. The described method enables a large-scale production of MoS₂ nanotubes and their size control. X-ray diffraction, optical absorption and Raman spectroscopy, scanning electron microscopy with wave dispersive analysis, and transmission electron microscopy were used to characterize the starting Mo₆S₄I₆ nanowires and the MoS₂ nanotubes. The unit cell parameters of the Mo₆S₄I₆ phase are proposed. Blue shift in optical absorbance and metallic behavior of MoS₂ nanotubes in two-probe measurement are explained by a high defect concentration.     

A novel disubstituted Lindqvist-type polyoxomolybdate [Te2Mo4O19] supporting two organic vanadyl moieties: Synthesis, characterization, and crystal structure of {[V(2,2-bipy)2]2(4,4-bipy)[Te2Mo4O19]}

The first example of disubstituted Lindqvist-type polyoxomolybdate {[V(2,2-bipy)₂]₂(4,4-bipy)[Te₂Mo₄O₁₉]} has been synthesized hydrothermally and characterized by elemental analyses, XPS, IR, TG-DTA and X-ray single crystal diffraction. The structural analysis shows that the neutral molecular unit [V(2,2-bipy)₂]₂[Te₂Mo₄O₁₉] consists of a novel Lindqvist-type polyanion [Te₂Mo₄O₁₉]⁶⁻ supporting two vanadyl moieties [V(2,2-bipy)₂]³⁺, and such neutral molecules are joined together by π − π stacking interactions between the pyridine groups to form a two-dimensional grid-like network with non-coordinating “guest” 4,4-bipys encapsulated.     

A hot hole-programmed and low-temperature-formed SONOS flash memory

In this study, a high-performance Ti_xZr_ySi_zO flash memory is demonstrated using a sol–gel spin-coating method and formed under a low annealing temperature. The high-efficiency charge storage layer is formed by depositing a well-mixed solution of titanium tetrachloride, silicon tetrachloride, and zirconium tetrachloride, followed by 60 s of annealing at 600°C. The flash memory exhibits a noteworthy hot hole trapping characteristic and excellent electrical properties regarding memory window, program/erase speeds, and charge retention. At only 6-V operation, the program/erase speeds can be as fast as 120:5.2 μs with a 2-V shift, and the memory window can be up to 8 V. The retention times are extrapolated to 10⁶ s with only 5% (at 85°C) and 10% (at 125°C) charge loss. The barrier height of the Ti_xZr_ySi_zO film is demonstrated to be 1.15 eV for hole trapping, through the extraction of the Poole-Frenkel current. The excellent performance of the memory is attributed to high trapping sites of the low-temperature-annealed, high-κ sol–gel film.