Crystallization of amorphous antimony films

Diffusion of the divalent impurities Mn²⁺, Ca²⁺, Cu²⁺, Fe²⁺, Co²⁺, Pb²⁺, Zn²⁺, Eu²⁺ and S^2- in sodium chloride and other alkali halide crystals has been studied by electron microscopy and diffraction. At temperatures in the range 100°–700°C the impurities diffuse to the surface and form oxides which in some cases are epitaxial. This distribution of the impurities on the surface is studied and is found to have a strong influence on the overgrowth of other epitaxial deposits.     

Crystallization of amorphous antimony films deposited onto glass substrates in ultrahigh vacuum

The crystallization of amorphous antimony (a-Sb) films deposited onto glass substrates in an ultrahigh vacuum of 10^?6?10^?7 Pa is investigated through in situ observation with an optical microscope camera. In comparison with the results for deposition in a conventional vacuum of 10^?4?10^?5 Pa, a marked reduction is observed in the critical thickness d_c for crystallization. For thicknesses less than the previous d_c value of about 250 Å, the dependence of the crystallization rate on the thickness is found to weaken drastically and the activation energy of the atoms for crystallization to increase. The antimony crystallites which nucleate in such thin a-Sb films do not take a simple spherical form.     

Crystallization of amorphous Al-Cu films

Quench-condensed (- 160°C) Al-Cu films in the composition range from 19% to 50% Cu were heated to room temperature and annealed up to 300°C. The temperature dependence of the resistivity and the temperature coefficient of the resistivity were observed during various cycles of temperature changes. The films are amorphous at the condensation temperature. Phase transitions which occur as the temperature is increased initiate sharp decreases in the resistance. Investigations of the film structure and composition were carried out with an electron microscope (transmission electron microscopy, electron diffraction, scanning transmission electron microscopy and X-ray microanalysis). The results could be clearly related to the phase transitions as observed via the resistance changes during annealing. For film compositions below 37.4% Cu the phase transition is determined by a eutectic crystallization into two phases. For larger copper contents, an intermediate single- phase state is produced first during the transition by polymorphous crystallization and is succeeded by a multiphase stable state.     

Electrical resistivity of amorphous antimony trisulphide films

The electrical resistivity of amorphous antimony trisulphide films was investigated in the temperature range from 0 to 200° C. The temperature dependence of the resistivity follows the ordinary semiconducting behaviour above room temperature. The electrical band gap was found to be consistent with a mobility gap. By annealing the conductivity reduces and the slope of the conduction is increased indicating that the mobility gap is appreciably enhanced by annealing.     

Crystallization kinetics of magnetron-sputtered amorphous CoNbZr thin films

For non-isothermal and isothermal annealing, the crystallization kinetics of magnetron sputtered Co_85.5Nb_8.9Zr_5.6 amorphous alloy thin films have been investigated by differential scanning calorimetry measurements. As a result, in the case of non-isothermal crystallization, one distinct exothermic peak is observed at 470 °C, which is due to the crystallization of hcp α-Co. With the Kissinger method, the apparent activation energy was obtained to be 99.82 kJ/mol. By using the Deloy-Ozawa method, the local activation energy of non-isothermal crystallization was calculated. For isothermal crystallization, the Avrami exponents were determined by means of the Johson-Mehl-Avrami equation, which is in the range of 1.19-1.37. Based on an Arrhenius relationship, the local activation energy was analyzed, which yields an average value E_c=88.51 kJ/mol. Finally, the local Avrami exponent was used for discussing the details of the nucleation and growth behaviour during the isothermal crystallization.     

Crystallization kinetics of amorphous Ga-Sb films extended for phase-change memory

Performance of phase-change materials based on Ga-Te-Sb was found getting better with decreasing Te content in our earlier studies. We concerned much properties of Te-free, Sb-rich binary Ga-Sb, which has been known to possess extremely fast crystallization behavior. Non-isothermal and isothermal crystallization kinetics of amorphous Sb-rich Ga-Sb films were explored by temperature dependent electrical resistance measurements. The crystallization temperature (183 to 261 degrees C) increases with decreasing Sb content (91 to 77 at%). The activation energy and rate-factor vary with Sb contents and reach the maximum at Ga19Sb81. The kinetic exponent is smaller than 1.5 at Sb < 85 at% denoting that the mechanism is one-dimensional crystal-growth from nuclei. The temperature corresponding to 10-year data-retention, evaluated from films, is 180 degrees C (Ga19Sb81) and 137 degrees C (Ga13Sb87), respectively. We verified memory performance using test-devices made of Ga16Sb84 working at voltages with 100 ns pulse-width.     

Dependence of the crystallization rate of vacuum-deposited amorphous antimony films on the film thickness

The crystallization rate of vacuum-deposited amorphous antimony (a-Sb) films was investigated as a function of the film thickness d. Experimental plots of the observed growth rate v against d^-1 for systems such as Sb/glass and Sb/Ge show that the relationship between v and d^-1 are convex towards the origin. Such a feature is well interpreted by a model in which

$\text{v=}\text{1}\text{d}\text{∫}\text{d}\text{0}\text{u}\text{d}\text{z}$

where u is the actual growth rate of the crystallite in the a-Sb film and z the distance from the film surface adjacent to the substrate. The quantity u is assumed to vary as follows: u = αzⁿ + u_s when 0 ? z ? d_s0, u = u_i when d_s0 ? z ? d ? d_v0 and u = β(d ? z)ⁿ + u_v, when d ? d_v0 ? z ? d where $\text{α =}\text{(u}{}_{\mathrm{i}}\text{? u}{}_{\mathrm{<mtext>s</mtext>}}\text{)}\text{d}{}_{\mathrm{<mtext>s</mtext><mtext>0</mtext>}}{}^{\mathrm{n}}$, $\text{β =}\text{(u}{}_{\mathrm{i}}\text{? u}{}_{\mathrm{<mtext>v</mtext>}}\text{)}\text{d}{}_{\mathrm{<mtext>v</mtext><mtext>0</mtext>}}{}^{\mathrm{n}}$, d_s0 and d_v0 are thickness of surface regions near the substrate and the vacuum respectively, u_i is the growth rate inside the film, u_s and u_v are the rates at surfaces adjacent to the substrate and the vacuum respectively and n an adjustable numerical parameter. As a typical example, for the Sb/Ge system at 30°C, u_i, u_s and u_v are estimated to be 139 μm s^-1, 25.4 μm s^-1 and 0.2 μm s^-1 respectively and d_s0 and d_v0 to be 133 Å and 143 Å respectively with n = 3.     

Structure and electrical properties of vacuum-deposited antimony telluride thin films on an amorphous substrate

Sb₂Te₃ thin films, 50–109 nm thick, have been prepared by vacuum evaporation on to quartz substrates. Electrical properties of as-deposited and annealed films show that the activation energy is thickness dependent. Optical measurements indicate that there is an indirect transition having an energy of 1.9 eV. Transmission electron micrographs show the fine grains of the deposit.     

Crystallization of amorphous Ge films induced by semiconductor diode laser annealing

Crystallization of amorphous Ge (a-Ge) films induced by semiconductor diode laser (SDL) irradiation has been investigated. 500-nm-thick a-Ge films are crystallized by scanning 807 nm CW SDL light focused to 4.0 × 0.1 mm² with the scanning speed (v) ranging from 100 to 350 mm/s. From X-ray diffraction and Raman scattering spectra, it is confirmed that the films crystallized at v = 100 mm/s show [220] preferential orientation with no residual amorphous component. On the basis of in-situ monitoring, it has been confirmed that a-Ge films annealed at a v higher than 200 mm/s are transformed to crystalline phase via solid phase crystallization, while films annealed with v lower than 170 mm/s are melted and recrystallized.     

化学沉淀法制备的α-Fe2O3非晶纳米线的晶化研究

以AAO为模板,采用化学沉淀法制备α-Fe2O3纳米线,经TEM和XRD分析表明,所制备的α-Fe2O3纳米线长度约为5 μ m,直径约为40～50nm,且为非晶态,该非晶纳米线的晶化温度约为850℃,明显高于α-Fe2O3纳米粉体的晶化温度.     

Estimation of density changes associated with growth in vacuum-deposited amorphous films of antimony

Amorphous antimony films consisting of separate islands were deposited onto SiO_x and GeO_x film substrates at room temperature in a vacuum of 10^-5 Torr. By comparison of the interferometrically determined thickness and the total mass of incident vapour determined with a quartz oscillator, it was found that a sudden change in film density occurs at a certain film thickness d₀. Another change in film density, which is gradual, occurs in the vicinity of a certain thickness $\text{d}{}_{\mathrm{<mtext>c</mtext>}}\text{(d}{}_{\mathrm{<mtext>c</mtext>}}\text{\&\#62; d}{}_{\mathrm{<mtext>0</mtext>}}\text{)}$. The change at d₀ is caused by the coalescence of neighbouring islands. The change at d_c, at which the coalescence of amorphous islands is almost completed, is associated with crystallization.     

准分子激光引起的非晶硅薄膜晶化行为的研究

利用KrF准分子激光对非晶硅薄膜的表层进行了晶化.研究了激光能量密度和照射脉冲数对薄膜结晶度的影响,并对晶化后薄膜的形貌和结构进行了表征.结果表明:该非晶硅薄膜晶化阈值约为110 mJ/cm2,且不受照射脉冲数的影响;激光能量密度是影响薄膜结晶度的首要因素,但在较低的能量密度时,增加照射脉冲数也会显著的提高薄膜结晶度;结构及形貌表征发现,薄膜晶化层厚度约为400～500 nm,平均晶粒尺寸为30～50 nm.     

Crystallization process on amorphous Mg-Ga-Sn system

The crystallization processes on Mg_81.09Ga_18.91 and Mg_80.50Ga_17.76Sn_1.67 amorphous samples were studied by means of X-ray diffraction and electrical resistivity isothermal measurements. A small amount of Sn added to the binary eutectic was found to modify the crystallization products and the evolution time. Crystallization activation energies were estimated.     

Crystallization behaviour of amorphous SiC films prepared by r.f. sputtering

The crystallization behaviour of amorphous SiC (a-SiC) films prepared by r.f. diode sputtering was studied using IR measurements and transmission electron microscopy. The absorption band at around 800 cm^-1 in the IR spectrum became sharper and more intense when a sample was annealed above 1000°C, corresponding to the phase transition in the film from amorphous to polycrystalline β-SiC. From cross-sectional transmission electron microscopy observations, crystallization occured homogeneously in the film. The crystallization behaviour was independent of the film thickness and the substrate temperature during preparation. The measured overall activation energy of crystallization of a-SiC films is about 5.0 eV.     

Crystallization study of chemically vapour-deposited amorphous silicon films by in situ x-ray diffraction

The solid phase crystallization kinetics of chemically vapour-deposited amorphous silicon films were studied by in situ X-ray diffraction. We determined the crystalline volume directly from the Bragg peak intensities at various times during isothermal annealing in the temperature range 578 °C < T < 658 °C. From these experiments we deduced that the crystallization was due to nucleation predominantly at the substrate-film interface followed by crystal growth perpendicular to this interface. The crystal growth rate was thermally activated with an activation energy E_v of 3.1 eV. A strong 〈111〉 preferred orientation of the growing polycrystal was observed and the grain size remained constant at about 60 nm. Evidence of stresses at the amorphous-crystalline interface during the early stages of crystallization was observed. A comparison with previous conductivity measurements is also carried out.     

Crystallization of amorphous indium zinc oxide thin films produced by radio-frequency magnetron sputtering

In this work we studied indium zinc oxide (IZO) thin films deposited by r.f. magnetron sputtering at room temperature. The films were annealed at high temperature (1100 K) in vacuum, and the oxygen exodiffusion was monitored in-situ. The results showed three main peaks, one at approximately 600 K, other at approximately 850 K and the last one at 940 K, which are probably from oxygen bonded in the film surface and in the bulk, respectively. The initial amorphous structure becomes microcrystalline, according to the X-ray diffraction. The electrical conductivity of the films decreases (about 3 orders of magnitude), after the annealing treatment.This behavior could be explained by the crystallization of the structure, which affects the transport mechanism. Apart from the changes in the material structure, a small variation was observed on the absorption coefficient.