Characterization of ion implantation through thin Ti metal layers on Si

Ion beam mixing of thin Ti films deposited on Si is investigated and its effect during subsequent thermal sintering determined. Both inert (Xe⁺) and dopant (As⁺) ions are used to intermix the metal films and Si substrate. The morphology of the suicide layer formed by this process and the structure of the silicide/Si interface is shown to be independent of the specific ions used for mixing. The structural differences observed are correlated to the electrical resistivity of the films. Transmission electron microscopy (TEM) and Rutherford backscattering spectroscopy (RBS) including ion channeling are used to characterize the films.     

Dopant incorporation in thin strained Si layers implanted with Sb

The effect of tensile strain on Sb incorporation in Si and its activation during post-implantation annealing has been studied by a combination of Rutherford backscattering/channeling spectrometry, secondary ion mass spectrometry, X-ray diffraction and 4-point probe measurements. Our results show that, for Sb implanted samples a tensile strain has an important role for dopant behavior. Particularly, increasing the tensile strain in the Si layer from 0 to 0.8% leads to an enhancement of the fraction of incorporated Sb atoms in substitutional sites already during implantation from ~ 7 to 30%. Furthermore, 0.8% strain in antimony doped Si gives ~ 20% reduction in the sheet resistance in comparison to the unstrained sample.     

Mechanical spectroscopy of thin layers of PPV polymer on Si substrates

The vibrating reed technique with electro“static” excitation and optical detection has been applied to investigate thin layers of poly-phenylene-vinylene, deposited by spin coating onto microfabricated Si cantilevers, during temperature cycling programs between 90 and 540 K at a rate of 1 K/min. From the vibration frequencies the Young’s modulus of the film can be estimated to be about 10 MPa at room temperature in the precursor phase (if prepared from a solution in toluene), which increases by conversion to the conjugate bonded polymer to about 50 MPa. The temperature dependence of internal friction reveals the processes of γ relaxations (crankshaft motion of side branches in the precursor) and β-relaxation (movements of a few monomer blocks in the polymer chain), as well as peaks indicating the structural transformations during conversion, and possibly a glass transition in the amorphous precursor phase. After conversion only the β-relaxation persists.     

Solid phase reactions between Fe thin films and Si-Ge layers on Si

Solid phase reactions in Fe thin films on epi-Si_0.8Ge_0.2, poly-Si_0.7Ge_0.3, a-Si_0.8Ge_0.2, and a-Si_0.7Ge_0.3 layers on silicon have been investigated. The as-deposited samples were in situ annealed in the ultrahigh vacuum chamber at 400-800 °C for 30 min. The island structure was found to cause the abrupt increase in the sheet resistance of the annealed Fe/SiGe samples at 700-800 °C. The formation of FeSi islands containing a small amount of Ge is attributed to the preferential reactions of Fe with Si to Ge. As the annealing temperature was raised to 800 °C, the Fe(Si_1−xGe_x) phase is the only phase found in the annealed Fe/epi-Si_0.8Ge_0.2 and Fe/poly-Si_0.7Ge_0.3 samples. On the other hand, at the annealing temperature above 700 °C, the β-Fe(Si_1−xGe_x)₂ phase was observed in the annealed Fe/a-Si_0.8Ge_0.2 and Fe/a-Si_0.7Ge_0.3 but the Fe(Si_1−xGe_x) is still the dominant phase. The results indicate that the formation of Fe disilicide was retarded by the presence of Ge atoms.     

Metal-induced crystallization of amorphous Si thin films assisted by atomic layer deposition of nickel oxide layers

Atomic layer deposition (ALD) of nickel oxide was applied to the nickel-induced crystallization of amorphous Si thin films. The nickel-induced crystallization was monitored as a function of annealing temperature and time using Raman spectroscopy. Since Raman spectroscopy allows for the numerical quantification of structural components, the incubation time and the crystallization rates were estimated as functions of the annealing temperature. The spatial locations of a nickel-based species, probably NiSi2, were investigated using X-ray photoelectron spectrometry. The formed NiSi2 seeds appeared to accelerate the crystallization kinetics in amorphous Si thin films deposited onto glass substrates. The ramifications of the atomic layer deposition are discussed with regard to large-panel displays, with special emphasis on the sophisticated control of the catalytic elements, especially nickel.     

Flux pinning by thin chromium layers

The flux pinning strength and upper critical field have been measured in multilayered evaporated films composed of thick layers of polycrystalline Pb-18% Bi alloy periodically interleaved with much thinner layers of chromium. The flux pinning strength of a single Cr layer with the applied magnetic field parallel to the layers is estimated to be at least 180 N/m² at a reduced field ofh=H/H _c2=0.7, and is independent of Cr layer thickness. The parallel flux pinning strength drops sharply, however, if the layer spacingd ₁ is reduced to less than 60 nm. The upper critical field with the applied field normal to the layers is slightly elevated for larged ₁ , but is strongly depressed ford ₁ <100 nm; the parallel upper critical field is independent ofd ₁ .This work was supported financially by the U.S. Air Force Office of Scientific Research through grants AFSOR-77-3107 and F44620-74-C-0019. This work benefited from the use of the facilities of the Materials Science Center at Cornell, which is funded by the U.S. National Science Foundation.     

Morphology and electronic structure of thin 3,4,9,10-perylenetetracarboxylic dianhydride layers on Si(001)

The growth of 3,4,9,10-perylenetetracarboxylic dianhydride on Si(001) was examined in the light of varying flux of impinging molecules. Using atomic force microscopy and synchrotron radiation photoelectron spectroscopy Vollmer-Weber growth mode was observed on a wide range of growth rates. The island size initially decreases rapidly with growth rate, for the low growth rate reaches a minimum, and then gradually increases. Polarization dependent photoemission indicates that the orientation of the molecules within the islands remains flat on the substrate.     

Nanostructure formation of Cu/Si(100) thin film induced by ion beam bombardment

A simple method for fabricating self-organized Cu nano-dots on Si(100) substrate by low energy Ar⁺ ion beam bombardment of a Cu thin film at room temperature over a large area is demonstrated. The morphological evolution has been investigated using scanning electron microscopy and atomic force microscopy. It was found that nano-ripple patterns formed on a Cu grain surface on a 110 nm thick polycrystalline Cu thin film under normal ion incidence. Uniformly distributed Cu nano-dots were obtained by bombardment of 55 nm thick nano-crystalline Cu thin films. The formation mechanism of the Cu nanostructures was discussed with the aid of numerical simulations using a modified damped Kuramoto–Sivashinsky equation.     

Polycrystalline Si1-x Ge x thin film deposition by rapid thermal chemical vapor deposition

Polycrystalline silicon germanium (poly-Si_1−xGe_x) thin films on a-Si film have been deposited by rapid thermal chemical vapor deposition (RTCVD) with SiH₄–GeH₄–H₂. Effect of GeH₄/SiH₄ and deposition temperature on stoichiometry (x), Si-Ge binding character, composition, hydrogen configuration, crystallinity, preferred orientation, grain size, and surface roughness of poly-Si_1−xGe_x films has been investigated. Poly-Si_1−xGe_x deposited on the substrate with amorphous silicon buffer layer on oxide shows better crystallinity and contains the less amount of oxygen than the one deposited directly on the oxide surface. At low temperature region, the Ge–H bond with the small amount of Si–H₂ bond is dominant but all hydrogen bonds are desorbed at high temperature. All films have polycrystalline phase and the grain size and (111) orientation increased with increasing deposition temperature in which Ge content also increases at the fixed gas flow rate of GeH₄ to total source gas. Poly-Si_1−xGe_x/Si thin film transistors (TFT) are fabricated and hydrogen during post-hydrogenation process preferentially is attached to Ge dangling bond and the TFT characteristics could be improved.     

Growth of InN layers on Si (111) using ultra thin silicon nitride buffer layer by NPA-MBE

Indium nitride (InN) epilayers have been successfully grown by nitrogen-plasma-assisted molecular beam epitaxy (NPA-MBE) on Si (111) substrates using different buffer layers. Growth of a (0001)-oriented single crystalline wurtzite-InN layer was confirmed by high resolution X-ray diffraction (HRXRD). The Raman studies show the high crystalline quality and the wurtzite lattice structure of InN films on the Si substrate using different buffer layers and the InN/β-Si₃N₄ double buffer layer achieves minimum FWHM of E₂ (high) mode. The energy gap of InN films was determined by optical absorption measurement and found to be in the range of ~ 0.73-0.78 eV with a direct band nature. It is found that a double-buffer technique (InN/β-Si₃N₄) insures improved crystallinity, smooth surface and good optical properties.     

Comparative study on phase formation in Al-Pd thin film by ion beam mixing and thermal annealing

Ion beam mixing and/or thermal annealing were conducted to study the phase formation and dissociation in Al-Pd thin films. The films were prepared by sequential evaporation, Ar⁺ ion mixed, annealed at 350 °C for 1 h under vacuum and then analysed by RBS, TEM and XPS. The intermetallic compounds formed by ion mixing alone are found to be Al₃Pd₂ and AlPd at a dose of 1.5 × 10¹⁶ Ar⁺ cm^–2. Thermal annealing after this radiation gave two new phases of Al₃Pd and Al₃Pd₅ in addition to Al₃Pd₂ and AlPd. For an as-annealed sample without Ar⁺ bombardment, the observed phases are Al₃Pd, Al₃Pd₂ and AlPd. The different behaviours in phase formation between ion beam mixing and thermal annealing are presented.     

Characterization of carbon thin films prepared by the thermal decomposition of spin coated polyacrylonitrile layers containing metal acetates

Polyacrylonitrile (PAN) layers were cast from dimethyl-formamide solutions onto quartz substrates by spin coating and subsequently annealed at up to 1000 °C in N₂ atmosphere. Carbonization was catalyzed by nickel or cobalt added to the solution as acetate salts. The synthesized films were approx. 970 nm thick and were characterized by Raman and infrared spectroscopy as well as thermogravimetric and electrical conductance measurements. We discuss the effects of carbonization temperature and metal concentration on the morphology, composition and electrical properties of the formed carbon layer. Increasing the amount of catalyst and the pyrolysis temperature was beneficial for the process and resulted in carbonaceous films with a higher degree of structural order as evidenced by the decreasing Raman I_D/I_G ratio and the increasing electrical conductivity of the films. Cobalt is a better catalyst for PAN carbonization than nickel as far as the structure of the product film is concerned.     

半导体Si(111)上电沉积NiFe缓冲层薄膜

采用电化学沉积法,在半导体硅片上制备了具有纳米晶粒尺寸的NiFe缓冲层薄膜,并确定了获得Ni80Fe20合金的工艺条件.由SEM形貌观测分析,当薄膜名义厚度＞25 nm时,可形成连续性镀层.I-t暂态曲线及STM结果表明,NiFe薄膜在低过电位下以三维岛状模式生长,在高过电位下以二维层状模式生长,其RMS表面粗糙度最小值仅为0.5 nm.XRD结果表明,薄膜为面心立方Ni基固溶体结构,并具有明显的(111)晶面择优取向.当薄膜组成为Ni80Fe20时,各向异性磁电阻效应(AMR)最大,AMR值为1.8%.