Energy barriers at the interfaces in the MIS system Me-Yb2O3-Si

The electrophysical properties of silicon MIS structures with ytterbium oxide as the insulator are investigated. It is established that the electrical conductivity of the MIS structures are described by a Poole-Frenkel mechanism. The capacitance-voltage curves are used to measure the trapped charge in the insulator and the density of surface states. The energy barriers for electrons at the interfaces are determined by the method of internal photoemission of charge carriers into the insulator. The parameters of deep electron traps in ytterbium oxide are investigated. Zh. Tekh. Fiz. 69, 60–64 (April 1999)     

Characterization of MOVPE-grown GaAs layers by C-V analysis

A computer simulation study of the capacitance of a surface space charge layer in undoped n-GaAs grown by metalorganic vapour phase epitaxy is presented. The effect of the deep donor level EL2 on the surface capacitance of epilayers with an ideal free surface is estimated. In order to approach the as-grown layer surface the model used is extended considering MIS and Schottky-barrier structures and their voltage-capacitance curves are analysed. The theoretical C-V dependences are compared with experimental C-V curves of a real structure including N⁺-GaAs substrate, undoped n-GaAs epitaxial layer containing EL2 levels and thin native oxide. Conditions are determined at which the EL2 levels as well as the native oxide film may influence the capacitance characteristics.     

Isotope shifts and hyperfine structure of erbium,dysprosium, and gadolinium by atomic-beam diode-laser spectroscopy

A commercial diode laser system, without external frequency stabilization, has been used to study the isotope shifts and hyperfine structure in a near infrared transition of erbium, dysprosium and gadolinium. Specific mass shifts and relative values for the change in the radial nuclear charge parameters of the isotopes were obtained for erbium and dysprosium that compare well with literature values. The hyperfine structure constants measured for erbium fell within the range predicted from the results of other workers. The isotope shifts in the gadolinium transition investigated were too small for the spectrum to be resolved.     

Charge distribution in a MIS insulator from spectral characteristics of photoemission current

The field dependence of photoemission currents in a MIS structure was derived for the case when the space charge is randomly distributed over the insulating layer. It was found analytically that the position of the top of the potential barrier for electrons photoinjected from the gate into the insulator is defined by the derivative of this barrier with respect to the external field strength. A method for correctly determining the space charge profile in a MIS insulator is suggested. The profile is derived from a family of spectral characteristics taken at different gate voltages. The method is especially suitable for profiling the negative charge in MIS insulators.     

Isotope shifts and hyperfine structure of natural dysprosium

Isotype shifts and hyperfine structure measurements for five transitions in natural dysprosium have been performed using a CW tunable dye laser and a collimated atomic beam. The consistency of experimental isotope shifts is tested and values of the change in rms radius of the nuclear charge distribution are calculated.     

Quantitative infrared study of ultrathin MIS structures by grazing internal reflection

A very sensitive reflection technique well suited for infrared investigations of thin MIS structures is introduced. With this technique a nearly saturating reflectance drop from the Si-O vibration of a 1.3 nm oxide on silicon within a MIS structure was measured at 1240 cm^–1. The analytic discussion of the sensitivity amplification of this technique shows that for silicon oxide a sensitivity amplification by a factor of 600 per reflection is feasible over the sensitivity of a transmission measurement. The analytic discussion is verified experimentally for the case of 12 nm silicon nitride film. A method that allows one to determine bond concentrations of thin films within MIS structures is given and tested for the case of hydrogen bonds in silicon nitride.     

Charge storage characteristics in Al/AlN/Si metal–insulator–semiconductor structure based on deep traps in AlN layer

Charge storage characteristics in an Al/AlN/p-Si metal–insulator–semiconductor (MIS) structure have been investigated by capacitance–voltage and long-term capacitance measurements. Good program/erase behavior is observed in the AlN/Si structure, which is attributed to the trapping and detrapping of charges in deep traps of the AlN layer. In the long-term retention mode, a clear memory window is found 2000 s after removing a program/erase voltage of ±3 V, indicating good charge retention capability of the MIS structure. Further investigation shows that for a program pulse width of 500 ms, the charge storage does not occur when the pulse amplitude is smaller than a threshold value of ∼1 V. The trapped charge density increases linearly with increase of the pulse amplitude (>1 V) and tends to saturate at 2.5 V. With increasing program pulse width, the trapped charged density increases a little more than logarithmically. PACS 73.40.Kp; 72.20.Jv; 71.55.Eq     

Spectroscopic Properties of Dysprosium Oxide Containing Lithium Borate Glasses

In this paper, we discussed the optical and luminescence properties of dysprosium oxide containing lithium borate glasses along with the structural properties. Absorption spectra of these glasses show strong absorption bands in ultraviolet and visible regions. Increase in dysprosium oxide content decreases in optical energy band gap, which is explained on the basis of glass structure. These glasses show bright blue emission at 482 nm and yellow emission at 573.5 nm due to ⁴ F _9/2  →  ⁶ H _15/2 and ⁴ F _9/2  →  ⁶ H _13/2 transitions of dysprosium ions.     

AlN-Si(111)异质结构界面陷阱态研究

利用Al_AlN_Si(111) MIS结构电容_频率谱研究了金属有机化学气相沉积法生长的 Si 基AlN的AlN_Si异质结构中的电荷陷阱态. 揭示了AlN_Si异质结构界面电荷陷阱态以及A lN层中的分立陷阱中心. 结果指出：AlN层中存在E_t-E_v=2.55eV的分立陷阱中心；AlN_Si界面陷阱态在Si能隙范围内呈连续分布，带中央态密度最低，N_ss为8×10^11eＶ^-1cm^-2，对应的时间常数τ为8×10^-4s ，俘获截面σn为1.58×10^-14cm^2；在AlN界面层存在三种陷阱 态，导致Al_AlN_Si异质结构积累区电容的频散. 关键词： 界面陷阱态 AlN-Si 电容-频率谱     

Partial Phonon Density of States of Dysprosium and its Compounds Measured Using Inelastic Nuclear Resonance Scattering

Inelastic nuclear resonance scattering measurements, utilizing a submilli eV monochromator, were performed on natural Dy metal, dysprosium oxide, and intermetallic Laves and Chevrel phase dysprosium compounds. The inelastic spectrum directly yields the partial phonon density of states, and thus provides a wealth of information about the modes of vibration occurring in a lattice at the Mössbauer Dy site. The extraction of the partial phonon density of states from a broad range of materials containing dysprosium demonstrates the feasibility of material science studies.     

Photoluminescence study on amino functionalized dysprosium oxide–zinc oxide composite bifunctional nanoparticles

An organic dispersion of 9–15 nm size stable dysprosium oxide incorporated zinc oxide nanocomposites exhibiting luminescence in the visible region has been synthesised by a wet chemical precipitation technique at room temperature. Tetraethoxysilane TEOS [(C₂H₅O)₄Si], (3-aminopropyl) trimethoxysilane (APTS) and a 1:1 mixture of TEOS–APTS have been used as capping agents to control the particle size as well as to achieve uniform dispersion of composite nanoparticles in methanol medium. X-ray diffractometer (XRD) analysis reveals the formation phase of amino-functionalised colloidal dysprosium oxide incorporated ZnO composite nanoparticles to be of zincite structure. The Transmission Electron Microscopy (TEM) images show that the particles are spheroids in shape, having average crystalline sizes ranging from 9 to 15 nm. The photoluminescence (PL) observed in these composites has been attributed to the presence of near band edge excitonic emission and existence of defect centres. The time correlated single photon counting studies of the composite nanoparticles exhibited three decay pathways. The enhanced PL emission intensity of solid state fluorescence spectra of samples is attributed to the absence of vibrational relaxation process.     

Characterization of Si-added aluminum oxide (AlSiO) films for power devices

Synthesis of Si-added aluminum oxide (AlSiO) films is attempted as an insulating film with both a wide bandgap and a high dielectric constant. Electrical characteristics of AlSiO films are investigated. Leakage current of the AlO film is suppressed by Si addition and is minimized with Si composition ratio of 12%. Capacitance versus voltage (C-V) measurements are carried out for Au/AlSiO/Si MIS structure. Both flat band shift and hysteresis of the C-V characteristics are suppressed by Si addition. A low leakage current is demonstrated for Au/AlSiO/n-SiC MIS structure.     

激光诱导荧光光谱分析法研究(Ⅸ)Dy-AA-TOPO-SLS的发光机理及分析应用

本文采用自己组装的激光诱导荧光光谱测定装置,研究了镝-乙酰丙酮-三正辛基膦化氧(Dy-AA-TOPO)体系在表面活性剂十二烷基磺酸钠(SLS)存在时的吸收光谱特性和激光诱导发光光谱特性,首次在室温测得AA的磷光发射.并从配体、中心离子的化学性质和所形成配合物的对称性及它们的光谱能级等方面综合考虑,提出配合物体系的发光机理和荧光发射过程中的能量传递方式.共存离子对配合物体系荧光发射强度的影响表明,在一定浓度范围内,某些稀土和非稀土离子可产生荧光增强作用,即“协同发光”效应.拟定出测定痕量镝的激光诱导荧光分析方法,对于单个激光脉冲产生的荧光,镝的工作曲线的线性范围为1-200ppb.用于高纯氧化钇中痕量镝的测定,获得了满意的结果.     

Ordered charge asphericity around dysprosium and structural deformation in DyB2C2

The orbitally ordered phase of DyB2C2 has been studied by nonresonant x-ray diffraction with high-brilliance synchrotron radiation. From the condition of diffraction, the symmetry property of the charge distribution around dysprosium has been concluded at the quadrupolar level. The quantitative inspection, furthermore, indicates that the observed signals cannot be interpreted as arising only from the 4f electrons of dysprosium responsible for the ordering; instead, the experiment can be described rather well by considering a distortion of the metaloid network concomitant with the ordering.     

The thermodepolarization charge and the variation of effective charge in an MIS structure with two ohmic electrodes

An analysis is made of the relation between the thermodepolarization charge (Q_TSD), the variation in the effective charge of an MIS structure during thermodepolarization (Q_SS), and the total moving charge (Q_o). The effect of the fixed charge on the character of the moving-charge flow is shown. It is noted that the evaluation of Q_o from the magnitude of the thermodepolarization charge is not unique.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika. No. 3. pp. 66–70, March, 1978.     

Resonance charge relaxation in physical barrier layers

It is shown experimentally that the space charge domain (SCD) of a MIS structure can be described as a layer-macrorelaxer by applying the appropriate formula for the Schottky barrier. The maximal time of the transient t_C (the saturation time t_CH) of the change in MIS-structure capacitance upon imposition of a sufficiently large rectangular depleting voltage pulse is expressed by the formula mentioned. A new method is correspondingly proposed for determining the ionization energy of bulk centers responsible for this relaxation. A comparison with data in the literature is presented and the prospects for developing representations on resonance charge relaxation in barrier layers is indicated.     

Metallization of grafted silicon surfaces: Sputtering-related damage effects

Metal sputtering is known to affect metal-insulating-semiconductor (MIS) devices where the insulator is an organic monolayer grafted onto crystalline substrates. We comparatively discuss current-voltage characteristics in MIS devices, where the insulating layer is either a thin oxide layer or an organic monolayer covalently grafted onto single-crystal silicon. Variation of the sputtering geometry from on-axis to off-axis configuration is analyzed to compare differences between them, obtaining the reduction of damages in the oxide layer accordingly to the supposed conduction mechanism, but no changes in organic layer of aliphatic molecules. Effects of ultraviolet radiations, already present during metal deposition, are also discussed.     

Charge degradation of an mis system with nonuniform tunnel-injected current density distribution

Using a model of the charge state of a metal-insulator-semiconductor (MIS) system with a nonuniform distribution of tunneling-injected current, we have investigated charge degradation of the dielectric in the neighborhood of defects (with a lowered semiconductor-insulator potential barrier) and a thinner insulator film. We determined the character and change in the charge state and the current load of defect regions during the initial stages of injection. We determined the dependence of the intensity of degrading processes on the ratio of the defect area to the defect-free portion of the structure. We show that a localized increase in tunnel current density is possible around a defect. Kaluzhskii Branch of the N. E. Bauman State Technical University, Moscow. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 42, No. 1, pp. 49–54, January, 1999.     

Capacitance-voltage characteristic of mis structures with allowance for depletion

In the ideal MIS structure considered, then-type semiconductor is uniformly doped. Allowance is made for the fact that the minority carriers in the space-charge region are in a nonequilibrium state when a high-frequency measuring signal is applied to the MIS structure. An expression is obtained for the high-frequency capacitance with allowance for depletion. It is shown that the partial ionization of the impurities must be taken into account over a wide range of donor densities. The high-frequency capacitance-voltage characteristic has been observed to have a minimum in the inversion mode. An expression is presented for the analytical determination of the minimum capacitance in the inversion mode. At donor densities higher than 10¹⁶ cm⁻³ the capacitance-voltage characteristic displays a maximum near the potential of flat bands; the maximum is due to the contribution of the charge transfer of donor levels to the high-frequency capacitance. Tomsk State Academy of Control Systems and Radio Engineering. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 24–29, May, 1996.     

Electrical breakdown of dysprosium oxide films

The principal laws governing the electrical breakdown of dysprosium oxide films in silicon metal — insulator — semiconductor structures are investigated. The dependence of the breakdown field E_br on the rise rate of the voltage on the structure K_v, the temperature, the material and area of the electrode, and the humidity of the environment is studied. The dependence of the time delay of breakdown on the amplitude of a rectangular voltage pulse is investigated. It is established that the breakdown field increases linearly with log K_v for all insulator thicknesses, and the saturation of E_br is observed at K_v>10⁵ V/sec. It is found that E_br does not depend on the electrode material and decreases as the area of the electrode or the temperature is increased. The maximum breakdown field is determined: E _br ^max =14 MV/cm. The mechanism of the precursory stage of breakdown, i.e., the period of transient buildup of critical charge in the insulator, is discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 95–101, August, 1995.