Physical and electrical characteristics of a high-k Yb2O3 gate dielectric

High-k ytterbium oxide (Yb₂O₃) gate dielectrics were deposited on Si substrate by reactive sputtering. The structural features of these films after postdeposition annealing treatment were studied by X-ray diffraction and X-ray photoelectron spectroscopy. It is found that the Yb₂O₃ gate dielectrics annealed at 700 °C exhibit a larger capacitance value, a lower frequency dispersion and a smaller hysteresis voltage in C-V curves compared with other annealing temperatures. They also show negligible charge trapping under high constant voltage stress. This phenomenon is mainly attributed to the decrease in the amorphous silica thickness.     

Structural properties and electrical characteristics of high-k Tm2Ti2O7 gate dielectrics

In this article, the structural and electrical characteristics of high-k Tm₂Ti₂O₇ gate dielectrics deposited on Si (1 0 0) by means of reactive cosputtering were reported. The Tm₂Ti₂O₇ dielectrics annealed at 800 °C exhibited excellent electrical properties such as high capacitance value, small density of interface state, almost no hysteresis voltage, and low leakage current. This phenomenon is attributed to a rather well-crystallized Tm₂Ti₂O₇ structure and composition and a smooth surface observed by X-ray diffraction, X-ray photoelectron spectroscopy, and atomic force microscopy, respectively. This film also shows almost negligible charge trapping under high constant voltage stress.     

Effect of post-deposition annealing on structural and electrical properties of high-k HoTiO3 gate dielectrics

In this article, the authors developed a high-k HoTiO₃ gate dielectric deposited on Si (1 0 0) through reactive cosputtering. They found that the HoTiO₃ dielectrics annealed at 800 °C exhibited excellent electrical properties such as high capacitance value, small density of interface state, almost no hysteresis voltage, and low leakage current. This phenomenon is attributed to the decrease in intrinsic defect (related to oxygen vacancy) due to a rather well-crystallized HoTiO₃ structure and composition observed by X-ray diffraction, secondary ion mass spectrometry, and X-ray photoelectron spectroscopy, respectively.     

Influence of postdeposition annealing on structural properties and electrical characteristics of thin Tm2O3 and Tm2Ti2O7 dielectrics

We describe the structural properties and electrical characteristics of thin thulium oxide (Tm₂O₃) and thulium titanium oxide (Tm₂Ti₂O₇) as gate dielectrics deposited on silicon substrates through reactive sputtering. The structural and morphological features of these films were explored by X-ray diffraction, X-ray photoelectron spectroscopy, secondary ion mass spectrometry, and atomic force microscopy, measurements. It is found that the Tm₂Ti₂O₇ film annealed at 800 °C exhibited a thinner capacitance equivalent thickness of 19.8 Å, a lower interface trap density of 8.37 × 10¹¹ eV⁻¹ cm⁻², and a smaller hysteresis voltage of ∼4 mV than the other conditions. We attribute this behavior to the Ti incorporated into the Tm₂O₃ film improving the interfacial layer and the surface roughness. This film also shows negligible degrees of charge trapping at high electric field stress.     

Structural properties of Al2O3 dielectrics grown on TiN metal substrates by atomic layer deposition

We investigated on the structural properties of Al₂O₃ dielectrics grown on TiN metal substrates using an atomic layer deposition technique with tri-methyl-aluminum and either O₃ or H₂O as the precursor and oxidant, respectively. The structural and morphological features of these films were examined by atomic force microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy measurements. We find that Al₂O₃ dielectric films with the O₃ oxidant exhibit a rough morphology, a thick TiO₂ film, and a small amount of contaminants such as carbon and hydrogen. The reason for the rapid diffusion of oxygen atoms into the TiN lattice leads to the formation of TiO₂ layer on the TiN substrate. This is due to the higher oxidation potential of the O₃ compared to the H₂O.     

Annealing effects on the structure and electrical characteristics of amorphous Er2O3 films

Amorphous Er 2 O 3 films are deposited on Si (001) substrates by using reactive evaporation.This paper reports the evolution of the structure,morphology and electrical characteristics with annealing temperatures in an oxygen ambience.X-ray diffraction and high resolution transimission electron microscopy measurement show that the films remain amorphous even after annealing at 700 C.The capacitance in the accumulation region of Er 2 O 3 films annealed at 450 C is higher than that of as-deposited films and films annealed at other temperatures.An Er 2 O 3 /ErO x /SiO x /Si structure model is proposed to explain the results.The annealed films also exhibit a low leakage current density (around 1.38 × 10 4 A/cm 2 at a bias of 1 V) due to the evolution of morphology and composition of the films after they are annealed.     

Y掺杂Al2O3高k栅介质薄膜的制备及性能研究

利用射频反应共溅射方法制备了Y掺杂Al₂O₃电介质薄膜，用掠入射x射线衍射检测了薄膜的结构，用高分辨率扫描电子显微镜(HRSEM)、原子力显微镜(AFM)观察了薄膜断面和表面形貌，用高频C-V和变频C-V及J-V测量了样品的电学特性. 结果表明，Y的掺入使电介质薄膜的介电常数k有了很大提高(8.14—11.8)，并体现出了较好的介电特性. 分析认为：与氧具有较大电负性差的Y离子的加入，增大了薄膜中的金属—氧键(M—O)的强度；同时，Y的加入使Al₂O₃的结构和原子配位发生了改变，从而提高了离子极化对薄膜介电常数的贡献. 退火前后的XRD谱均显示薄膜为非晶态；HRSEM断面和AFM形貌像显示所制备的薄膜非常平整，能够满足器件要求. 关键词： 高k栅介质 掺杂氧化铝 射频反应溅射     

Stability of La2O3 and GeO2 passivated Ge surfaces during ALD of ZrO2 high-k dielectric

La₂O₃ grown by atomic layer deposition (ALD) and thermally grown GeO₂ are used to establish effective electrical surface passivations on n-type (1 0 0)-Ge substrates for high-k ZrO₂ dielectrics, grown by ALD at 250 °C substrate temperature. The electrical characterization of MOS capacitors indicates an impact of the Ge-surface passivation on the interfacial trap density and the frequency dependent capacitance in the inversion regime. Lower interface trap densities can be obtained for GeO₂ based passivation even though a chemical decomposition of the oxidation states occur during the ALD of ZrO₂. As a consequence the formation of a ZrGeO_x compound inside the ZrO₂ matrix and a decline of the interfacial GeO₂ are observed. The La₂O₃ passivation provides a stable amorphous lanthanum germanate phase at the Ge interface but also traces of Zr germanate are indicated by X-ray-Photoelectron-Spectroscopy and Transmission-Electron-Microscopy.     

Stabilization of a very high-k crystalline ZrO2 phase by post deposition annealing of atomic layer deposited ZrO2/La2O3 dielectrics on germanium

The impact of the ZrO₂/La₂O₃ film thickness ratio and the post deposition annealing in the temperature range between 400 °C and 600 °C on the electrical properties of ultrathin ZrO₂/La₂O₃ high-k dielectrics grown by atomic layer deposition on (1 0 0) germanium is investigated. As-deposited stacks have a relative dielectric constant of 24 which is increased to a value of 35 after annealing at 500 °C due to the stabilization of tetragonal/cubic ZrO₂ phases. This effect depends on the absolute thickness of ZrO₂ within the dielectric stack and is limited due to possible interfacial reactions at the oxide/Ge interface. We show that adequate processing leads to very high-k dielectrics with EOT values below 1 nm, leakage current densities in the range of 0.01 A/cm², and interface trap densities in the range of 2-5 × 10¹² eV⁻¹ cm⁻².     

强耦合磁失措自旋冰系统Dy2Ti2O7单晶生长和基本磁性质测量

利用红外光源浮区法生长出大尺寸、高质量的磁失措自旋冰化合物Dy₂Ti₂O₇单晶体.X射线衍射实验证实晶体具有面心立方结构，空间群为Fd3m，晶胞参数a＝1.0112(2) nm，［111］和［400］方向X射线衍射摇摆曲线半高宽分别仅为0.07°和0.05°.直流磁化率与温度关系测量给出晶体的Van Vleck顺磁因子为2.46×10^-5 m³/mol，有效磁矩μ_eff＝10.24(4)μ_B，Cure-Weiss温度Θ_CW＝1.1 K，揭示Dy₂Ti₂O₇具有弱的铁磁性.对磁性起源的综合分析表明，该自旋冰晶体磁性质主要来源于磁偶极相互作用，且相关最近邻长程偶极相互作用能量标度D_nn＝3.00 K. 关键词： 2Ti₂O₇')" href="#">Dy₂Ti₂O₇ 浮区法晶体生长 关联电子系统 自旋冰     

Chemical quenching of positronium in Fe2O3/Al2O3 catalysts

Fe₂O₃/Al₂O₃ catalysts were prepared by solid state reaction method using α-Fe₂O₃ and γ-Al₂O₃ nano powders. The microstructure and surface properties of the catalyst were studied using positron lifetime and coincidence Doppler broadening annihilation radiation measurements. The positron lifetime spectrum shows four components. The two long lifetimes τ₃ and τ₄ are attributed to positronium annihilation in two types of pores distributed inside Al₂O₃ grain and between the grains, respectively. With increasing Fe₂O₃ content from 3 wt% to 40 wt%, the lifetime τ₃ keeps nearly unchanged, while the longest lifetime τ₄ shows decrease from 96 ns to 64 ns. Its intensity decreases drastically from 24% to less than 8%. The Doppler broadening S parameter shows also a continuous decrease. Further analysis of the Doppler broadening spectra reveals a decrease in the p-Ps intensity with increasing Fe₂O₃ content, which rules out the possibility of spin-conversion of positronium. Therefore the decrease of τ₄ is most probably due to the chemical quenching reaction of positronium with Fe ions on the surface of the large pores.     

Synthesis and ion conductivity of (Bi2O3)0.75(Dy2O3)0.25 ceramics with grain sizes from the nano to the micro scale

Using (Bi₂O₃)_0.75(Dy₂O₃)_0.25 nano-powder synthesized by reverse titration co-precipitation method as raw material, dense ceramics were sintered by both Spark Plasma Sintering (SPS) and pressureless sintering. According to the predominance area diagram of Bi-O binary system, the sintering conditions under SPS were optimized. (Bi₂O₃)_0.75(Dy₂O₃)_0.25 ceramics with relative density higher than 95% and an average grain size of 20 nm were sintered in only 10 min up to 500 °C. During the pressureless sintering process, the grain growth behavior of (Bi₂O₃)_0.75(Dy₂O₃)_0.25 followed a parabolic trend, expressed as D² − D₀² = Kt, and the apparent activation energy of grain growth was found to be 284 kJ mol^− 1. Dense (Bi₂O₃)_0.75(Dy₂O₃)_0.25 ceramics with different grain sizes were obtained, and the effect of grain size on ion conductivity was investigated by impedance spectroscopy. It was shown that the total ion conductivity was not affected by the grain size down to 100 nm, however lower conductivity was measured for the sample with the smallest grain size (20 nm). But, although only the δ phase was evidenced by X-ray diffraction for this sample, a closer inspection by Raman spectroscopy revealed traces of α-Bi₂O₃.     

Synthesis and electrical properties of In2O3(ZnO)m superlattice nanobelt

One-dimensional（ID） In₂O₃（ZnO）_m superlattice nanobelts are synthesized by a chemical vapor deposition method.The formation of the In₂O₃（ZnO）_m superlattice is verified by the high-resolution transmission electron microscopy images.The typical zigzag boundaries could be clearly observed.An additional peak at 614 cm^-1 is found in the Raman spectrum,which may correspond to the superlattice structure.The study about the electrical transport properties reveals that the In₂O₃（ZnO）_m nanobelts exhibit peculiar nonlinear I-V characteristics even under the Ohmic contact measurement condition,which are different from the Ohmic behaviors of the In-doped ZnO nanobelts.The photoelectrical measurements show the differences in the photocurrent property between them,and their transport mechanisms are also discussed.     

Structural and optical properties of Er, Yb co-doped Y2O3 thin films

Thin Er³⁺, Yb³⁺ co-doped Y₂O₃ films were grown on (1 0 0) YAG substrates by pulsed laser deposition. Ceramic targets having different active ion concentration were used for ablation. The influence of the rare-earth content and oxygen pressure applied during the deposition on the structural, morphological and optical properties of the films were investigated. The films deposited at the lower pressure, 1 Pa, and at 1/10 Er to Yb doping ratio are highly textured along the (1 1 1) direction of the Y₂O₃ cubic phase. In addition to the crystalline structure, these films possess smoother surface compared to those prepared at the higher pressure, 10 Pa. All other films are polycrystalline, consisting of cubic and monoclinic phases of Y₂O₃. The rougher surface of the films produced at the higher-pressure leads to higher scattering losses and different behavior of the reflectivity spectra. Optical anisotropy in the films of less than 0.004 was measured regardless of the monoclinic structure obtained. Waveguide losses of about 1 dB/cm at 633 nm were obtained for the films produced at the lower oxygen pressure.     

Characterization of Y2O3 gate dielectric on n-GaAs substrates

Physical and electrical properties of sputtered deposited Y₂O₃ films on NH₄OH treated n-GaAs substrate are investigated. The as-deposited films and interfacial layer formation have been analyzed by using X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). It is found that directly deposited Y₂O₃ on n-GaAs exhibits excellent electrical properties with low frequency dispersion (<5%), hysteresis voltage (0.24 V), and interface trap density (3 × 10¹² eV⁻¹ cm⁻²). The results show that the deposition of Y₂O₃ on n-GaAs can be an effective way to improve the interface quality by the suppression on native oxides formation, especially arsenic oxide which causes Fermi level pinning at high-k/GaAs interface. The Al/Y₂O₃/n-GaAs stack with an equivalent oxide thickness (EOT) of 2.1 nm shows a leakage current density of 3.6 × 10⁻⁶ A cm⁻² at a V_FB of 1 V. While the low-field leakage current conduction mechanism has been found to be dominated by the Schottky emission, Poole-Frenkel emission takes over at high electric fields. The energy band alignment of Y₂O₃ films on n-GaAs substrate is extracted from detailed XPS measurements. The valence and conduction band offsets at Y₂O₃/n-GaAs interfaces are found to be 2.14 and 2.21 eV, respectively.     

Acid-base properties of Ni-MgO-Al2O3 materials

Ni-MgO-Al₂O₃ materials of different Ni/Mg ratios were prepared by the co-precipitation method. Acid-base properties of the samples after calcination and reduction were examined by the temperature programmed desorption of ammonia and carbon dioxide. Thermal treatment of the materials in air at 400 °C led to the formation of hydrotalcite-like phases. The increase of Ni/Mg ratio decreased the stability of the hydrotalcite structure. The number and the strength of acid and base sites were related to the Ni/Mg ratio and thermal treatment conditions of materials. It was found that the replacement of Ni with Mg decreased the acidity and increased basicity of the surface of oxide materials. Thermal treatment of the samples in hydrogen led to the structural changes. The presence of magnesia improved thermal stability. The ratio of the number of acid to base sites in the reduced samples gradually increased with the increase of magnesia content.     

CaCu3Ti4O12陶瓷的微观结构和电学性能

利用传统的固相反应工艺，在不同的烧结温度下制备了一系列的CaCu₃Ti₄O₁₂陶瓷样品，考察了其微观结构以及介电和复阻抗方面的电学性质.研究发现这些样品在微观结构方面可分为三种类型，高介电性与微观结构有着密切的关联性.室温下，样品的低频介电常数随陶瓷晶粒尺寸的增大而提高.随着测试温度的升高，不同微观结构类型的样品呈现出不同的电学性质的变化，但其中也存在着一些相同的特征.高温下，介电频谱呈现出一个低频介电响应和两个类Debye型弛豫色散，复阻抗谱呈现出三个Cole-Cole半圆弧.将实验上观测到的电学性质的起因归于陶瓷多晶微结构中的晶畴、晶界和晶粒内的缺陷. 关键词： 3Ti₄O₁₂')" href="#">CaCu₃Ti₄O₁₂ 微观结构 电学性质     

Magnetic and electrical properties of bulk BaTiO3+MgFe2O4 composite

BaTiO₃+MgFe₂O₄ material system was synthesized by hybrid chemical process using chlorides and nitrates of barium, titanium, iron, and magnesium. Magnetic properties of the composite samples measured as a function of annealing conditions indicated soft magnetic behavior. Saturation specific magnetization from 8 21 emu/g was observed for samples annealed at temperature between 950 and 1150 °C. Variation of specific saturation magnetization with respect to annealing temperature was related with the distribution of Fe cations in the tetrahedral and octahedral sites of MgFe₂O₄. Electrical properties of the samples annealed at different temperatures were measured to analyze the coexistence of ferroelectric phase. Dielectric constant varying from 15 to 200 with respect to frequency was observed for samples annealed from 950 to 1150 °C.     

The effect of Si surface nitridation on the interfacial structure and electrical properties of (La2O3)0.5(SiO2)0.5 high-k gate dielectric films

Thermal stability, interfacial structures and electrical properties of amorphous (La₂O₃)_0.5(SiO₂)_0.5 (LSO) films deposited by using pulsed laser deposition (PLD) on Si (1 0 0) and NH₃ nitrided Si (1 0 0) substrates were comparatively investigated. The LSO films keep the amorphous state up to a high annealing temperature of 900 °C. HRTEM observations and XPS analyses showed that the surface nitridation of silicon wafer using NH₃ can result in the formation of the passivation layer, which effectively suppresses the excessive growth of the interfacial layer between LSO film and silicon wafer after high-temperature annealing process. The Pt/LSO/nitrided Si capacitors annealed at high temperature exhibit smaller CET and EOT, a less flatband voltage shift, a negligible hysteresis loop, a smaller equivalent dielectric charge density, and a much lower gate leakage current density as compared with that of the Pt/LSO/Si capacitors without Si surface nitridation.     

The electrical properties of dielectric stacks of SiO2 and Al2O3 prepared by atomic layer deposition method

We produced dielectric stacks composed of ALD SiO₂ and ALD Al₂O₃, such as SiO₂/Al₂O₃, Al₂O₃/SiO₂, and SiO₂/Al₂O₃/SiO₂, and measured the leakage currents through the stacks in comparison with those of the single oxide layers. SiO₂/Al₂O₃ shows lowest leakage current for negative bias region below 6.4 V, and Al₂O₃/SiO₂ showed highest current under negative biases below 4.5 V. Two distinct electron conduction regimes are observed for Al₂O₃ and SiO₂/Al₂O₃. Poole-Frenkel emission is dominant at the high-voltage regime for both dielectrics, whereas the direct tunneling through the dielectric is dominant at the low-voltage regime. The calculated transition voltage between two regimes for SiO₂ (6.5 nm)/Al₂O₃ (12.6 nm) is −6.4 V, which agrees well with the experimental observation (−6.1 V). For the same EOT of entire dielectric stack, the transition voltage between two regimes decreases with thinner SiO₂ layer.