Flat Surface Morphology Research Articles

Electrical properties of metal-ferroelectric-insulator-semiconductor structure with Lanthanum Dysprosium Oxide and SrBi2Ta2O9

layer was prepared. The LDO thin film and the SBT film were deposited by using the sol-gel method. The sol-gel-derived LDO thin films on Si had very flat and smooth surface morphologies. The equivalent oxide thickness (EOT) values were about 10.1 nm, 12.5 nm, and 12.8 nm for 750 C, 800 C, and 850 C, respectively. Also, the relative dielectric constants of the 750 C-annealed, 800 C-annealed and 850 C-annealed LDO films were about 15.4, 12.5, and 12.2, respectively. On the whole, the leakage current densities showed good characteristics regardless of the annealing temperature. Especially, the leakage current property of the 850 C-annealed LDO film was visibly superior to those of the others at voltages over 6 V. The C-V characteristics of the Au/SBT/LDO/Si structure showed clockwise hysteresis loops, and the memory window width increased as the bias

Andreev reflection and spin polarization of SrRuO3 thin films on SrTiO3 (111)

Epitaxial SrRuO3 thin films with an extremely flat surface morphology suitable for the use in thin film heterostructures have been grown on SrTiO3 (111) substrates. The transport spin polarization was measured by point contact spectroscopy for SrRuO3 films on SrTiO3 (111) and comparable samples on SrTiO3 (001). The measured polarization for both types of samples is slightly smaller than previously measured by the same technique. Possible reasons for this difference are discussed.

Growth of semipolar {10$ \bar 1 $1} GaN from c ‐plane‐like sapphire sidewall of patterned n ‐plane sapphire substrate

AbstractThe direct growth of semipolar {10$ \bar 1 $1} GaN via metalorganic vapor phase epitaxy has been demonstrated using a patterned n ‐plane sapphire substrate with a c ‐plane‐like sidewall and terrace covered with a SiO2 mask. From X‐ray diffraction analysis, it was clear that a uniformly oriented {10$ \bar 1 $1} GaN layer was obtained. Scanning electron microscopy and atomic force microscopy measurements showed a flat surface morphology. The root‐mean‐square value of the {10$ \bar 1 $1} GaN layer is 0.7 nm over a 5 × 5 μm2 area. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Photoimaging of Self-Organized CaCO3/Polymer Hybrid Films by Formation of Regular Relief and Flat Surface Morphologies

Photoimaging of Self-Organized CaCO3/Polymer Hybrid Films by Formation of Regular Relief and Flat Surface Morphologies

Photoimaging of Self‐Organized CaCO3/Polymer Hybrid Films by Formation of Regular Relief and Flat Surface Morphologies

Was für ein Bild: Ein phototechnisch durch UV-Licht in einem reaktiven Polymer erzeugtes Bild wird in CaCO3-Kristallmorphologien überführt (siehe Bild). Die CaCO3-Kristallfilme verfügen über regelmäßige Reliefstrukturen und glatte Oberflächen und sind in den nicht bestrahlten bzw. den mit UV-Licht bestrahlten Bereichen der Polymermatrix selbstorganisiert.

XPS and AFM studies of surface chemistry and morphology of In 2O 3 ultrathin films deposited by rheotaxial growth and vacuum oxidation

In this paper, the results of XPS and AFM studies of the surface chemistry and morphology of In 2O 3 nanolayers obtained by rheotaxial growth and vacuum oxidation (RGVO) technology are presented. The ultrathin In films were deposited under UHV by thermal evaporation of indium pellets on the well defined Si substrate maintained at different temperatures. Optimal conditions to obtain the smallest grains and highest surface coverage have been determined, which was controlled by AFM, whereas the cleanness of deposited In nanolayers was controlled by XPS method. The ultrathin films of In 2O 3 (nm scale) were obtained in two ways, i.e. by oxidation of ultrathin films of In after their deposition, as well as by oxidation of In ultrathin films already during the deposition process. The XPS experiments showed that in both cases the obtained ultrathin films of In 2O 3 were almost stoichiometric. In turn, the AFM studies confirmed that only ultrathin films obtained during the simultaneous In deposition and oxidation exhibit almost flat surface morphology with average roughness at the level of about 0.85 nm.

Influence of growth temperatures on the quality of InGaAs/GaAs quantum well structure grown on Ge substrate by molecular beam epitaxy

Molecular beam epitaxy growth of an InxGa1−xAs/GaAs quantum well (QW) structure (x equals to 0.17 or 0.3) on offcut (100) Ge substrate has been investigated. The samples were characterized by atomic force microscopy, photoluminescence (PL), and high resolution transmission electron microscopy. High temperature annealing of the Ge substrate is necessary to grow GaAs buffer layer without anti-phase domains. During the subsequent growth of the GaAs buffer layer and an InxGa1−xAs/GaAs QW structure, temperature plays a key role. The mechanism by which temperature influences the material quality is discussed. High quality InxGa1−xAs/GaAs QW structure samples on Ge substrate with high PL intensity, narrow PL linewidth and flat surface morphology have been achieved by optimizing growth temperatures. Our results show promising device applications for III—V compound semiconductor materials grown on Ge substrates.

Mechanical and structural properties of high temperature a-ITO:Sm films deposited on polyimide substrate by DC magnetron sputtering

Amorphous ITO (a-ITO) films are well known to have very high potential application in flexible display because of their excellent surface morphology and good etchability, compared to polycrystalline ITO. However, there are some problem s such as relatively high resistivity and low durability under bending state. These poor electrical and mechanical properties of a-ITO films can be improved by elevating the substrate temperature. However, a-ITO films crystallized by heat treatment (approximately 170 °C) lose their advantages. Therefore, in this study, we try to improve the durability of a-ITO at the high temperature. ITO and Sm doped ITO (ITO:Sm) films were successfully deposited on polyimide (PI) substrates by DC magnetron sputtering using ITO targets containing different Sm ratios (doped-Sm: 0, 3, 5 and 7 wt.%). Film deposition and post-annealing were carried out at room temperature and different temperatures (170 °C and 200 °C), respectively, in a pure Ar gas atmosphere at 1.0 Pa for 1 h. The ITO:Sm films had an amorphous structure, good mechanical properties and a very flat surface morphology above the crystallization temperature of ITO films (approximately 170 °C). The mechanical properties of the ITO:Sm films were improved by increasing both Sm doping concentration and post-annealing temperature due to the alleviation of internal stress in the amorphous structure. The lowest resistivity (5.954 × 10 −4 Ω cm) was obtained for the amorphous ITO:Sm film deposited using the 3 wt.% Sm doped ITO target at 200 °C.

Growth and magnetism of low-temperature deposited Fe/Si(111) films as an intermediate layer for suppression of silicide formation

Low temperature (LT: 100 K) deposition of Fe on Si(111)7×7 surface effectively reduces Fe-silicide formation at the Fe/Si interface, as compared with conventional room temperature (RT) growth. The interface condition of 5–15 monolayers (ML) LT-Fe/Si(111) remains stable at least up to 350 K. Si segregation was observed after annealing at 400 K. LT-grown Fe films also reveal a relatively flat surface morphology with a roughness of 0.4–0.6 nm. Thus, LT-Fe films were suggested as an intermediate layer for the subsequent RT-growth of Fe. We use a single domain model of magnetic anisotropy to fit the magnetic coercivity evolution of n ML RT-Fe on 5 ML LT-Fe/Si(111). Accordingly, we deduce the surface and volume-contributed magnetic anisotropy for discussion.

Flattening Characteristics of Ni<SUB>20</SUB>Cr Thermal-Sprayed Coating Layers on Preheated SCM415 Substrates

The preheating effect of SCM415 steel substrates on the flattening behavior of Ni20Cr flame-sprayed particles was investigated in a temperature range from 278 K to 523 K. In the present study, we calculated the particle temperature and velocity distributions of the continuous and discrete phases before collision with the substrate by using a computational fluid dynamics (CFD) code of Fluent (ver. 6.3.26). Particle velocity and gas temperature decreased rapidly in the radial direction while the particles traveled toward the substrate, suggesting that substrate size and distance from the nozzle should be carefully controlled to improve coating quality. The conventional flame spray gun was used to accelerate molten particles and K-type thermocouples were used to monitor the substrate temperature during a preheating process. Commercially available nickel-based Ni20Cr particles with a mean diameter of 45 mm and 20 mm were used for experiments to examine the particle size effect on the coating characteristics. Herein we present FE-SEM images of coated layers on the substrates. As the substrate preheating temperature increased, the flatter surface morphology was seen at the interface between substrate and coating layer because of better wetting and corresponding higher shear adhesion strength. Moreover, the splat morphology was significantly dependent on the particle size. [doi:10.2320/matertrans.M2011068]

Molecular beam epitaxy growth of GaAs on an offcut Ge substrate

Molecular beam epitaxy growth of GaAs on an offcut Ge (100) substrate has been systemically investigated. A high quality GaAs/Ge interface and GaAs film on Ge have been achieved. High temperature annealing before GaAs deposition is found to be indispensable to avoid anti-phase domains. The quality of the GaAs film is found to strongly depend on the GaAs/Ge interface and the beginning of GaAs deposition. The reason why both high temperature annealing and GaAs growth temperature can affect epitaxial GaAs film quality is discussed. High quality In0.17Ga0.83As/GaAs strained quantum wells have also been achieved on a Ge substrate. Samples show flat surface morphology and narrow photoluminescence line width compared with the same structure sample grown on a GaAs substrate. These results indicate a large application potential for III—V compound semiconductor optoelectronic devices on Ge substrates.

Characteristics of amorphous Yb-doped ITO films deposited on polyimide substrate by DC magnetron sputtering

The ITO and Yb-doped ITO (ITO:Yb) films were deposited on polyimide (PI) substrates by DC magnetron sputtering using ITO targets (doped-Yb: 0, 0.57, 3.2 and 7.75 at.%) containing different Yb ratios. Film deposition and post-annealing were carried out at room temperature and different temperatures (170 °C and 200 °C), respectively, in a pure Ar gas atmosphere at 1.0 Pa for 1 h. The ITO:Yb films had a higher crystallization temperature than that of the ITO films, which was attributed to Yb 3+ atoms degrading the crystallinity of the ITO film. The ITO:Yb films also had good mechanical properties and a very flat surface morphology above the crystallization temperature of the ITO films (approximately 170 °C). The lowest resistivity of the polycrystalline ITO films obtained was 2.983 × 10 − 4 Ω cm at 200 °C. On the other hand, the amorphous ITO:Yb films deposited from the 3.2 at.% Yb-doped ITO target at 170 °C had the lowest resistivity of 4.672 × 10 − 4 Ω cm. The transmittance of all the ITO:Yb films was > 80% in the visible region.

Subnanometer-Thick PbS Film on Organic Substrate and Its Usage as Buffer for Homo- and Heteroepitaxial Overgrowth

We report on the fabrication of a subnanometer-thick epitaxial PbS film on polydiacetylene (PDA) substrate. The film is formed by cation-absorption in PbCl2 solution followed by sulfidation in mixed H2S/N2 gas, exhibiting a flat and smooth surface morphology. The strong adsorbate-surface interaction between the lead hydrolysis complexes and the carboxyl headgroups on the surface of PDA accounts for such a growth mode. We further demonstrate that such an ultrathin film can be used as a buffer layer for both homo- and heteroepitaxial growth of sulfide films. The X-ray and electron diffraction results reveal that the (001) planes of PbS are parallel to the surface of PDA and the (110) planes of PbS are parallel to the (110) planes of PDA.

Atomically Flat Silicon Surface and Silicon/Insulator Interface Formation Technologies for (100) Surface Orientation Large-Diameter Wafers Introducing High Performance and Low-Noise Metal–Insulator–Silicon FETs

Technology to atomically flatten the silicon surface on (100) orientation large-diameter wafer and the formation technology of an atomically flat insulator film/silicon interface are developed in this paper. Atomically flat silicon surfaces composed of atomic terraces and steps are obtained on (100) orientation 200-mm-diameter wafers by annealing in pure argon ambience at 1200 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">deg</sup> C for 30 min. Atomically flat surfaces with various terrace widths and step structures are observed by atomic force microscopy. It is found that the atomic terrace width changes widely with an off angle of the wafer surface from the (100) lattice plane. It is also found that the direction of the off angle significantly affects the atomically flat surface morphology, i.e., when the directions of the off angles are parallel to the <110> directions, the step structure is composed of alternating pairs of straight and triangular steps. When the directions of the off angles are parallel to the <100> directions, the step structure is composed of only straight steps. By precise control of the off angle and the direction toward the <100> directions for a 200-mm-diameter silicon wafer, we have succeeded in fabricating an atomically flat surface with straight atomic steps and a very uniform terrace width of 140-150 nm on the entire surface of a large-diameter silicon wafer. Furthermore, it is found that only radical-reaction-based insulator film formation technology, such as oxidation utilizing oxygen radicals carried out at a low temperature (400 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">deg</sup> C ), preserves the atomic flatness of the insulator film/silicon interface. Finally, when MOSFETs are fabricated with an atomically flat interface, they exhibit near ideal subthreshold swing factors, with much smaller fluctuation, extremely lower 1/ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> noise, and higher MOS dielectric breakdown field intensity compared with MOSFETs fabricated with conventional technologies.

Probing Surface-Adlayer Conjugation on Organic-Modified Si(111) Surfaces with Microscopy, Scattering, Spectroscopy, and Density Functional Theory

Highly conjugated molecules bound to silicon are promising candidates for organosilicon electronic devices and sensors. In this study, 1-bromo-4-ethynylbenzene was synthesized and reacted with a hydrogen-passivated Si(111) surface via ultraviolet irradiation. Through an array of characterization and modeling tools, the binding configuration and morphology of the reacted molecule were thoroughly analyzed. Atomic force microscopy confirmed an atomically flat surface morphology following reaction, while X-ray photoelectron spectroscopy verified reaction to the surface via the terminal alkyne moiety. In addition, synchrotron X-ray characterization, including X-ray reflectivity, X-ray fluorescence, and X-ray standing wave measurements, enabled sub-angstrom determination of the position of the bromine atom with respect to the silicon lattice. This structural characterization was quantitatively compared with density functional theory (DFT) calculations, thus enabling the π-conjugation of the terminal carbon atom...

Surface structure of Sn-doped In2O3 (111) thin films by STM

High-quality Sn-doped In2O3 (ITO) films were grown epitaxially on yttria stabilized zirconia (111) with oxygen-plasma assisted molecular beam epitaxy (MBE). The 12 nm thick films, containing 2–6% Sn, are fully oxidized. Angle-resolved x-ray photoelectron spectroscopy (ARXPS) confirms that the Sn dopant substitutes In atoms in the bixbyite lattice. From XPS peak shape analysis and spectroscopic ellipsometry measurements it is estimated that, in a film with 6 at.% Sn, ∼1/3 of the Sn atoms are electrically active. Reflection high energy electron diffraction (RHEED) shows a flat surface morphology and scanning tunneling microscopy (STM) shows terraces several hundred nanometers in width. The terraces consist of 10 nm wide orientational domains, which are attributed to the initial nucleation of the film. Low energy electron diffraction (LEED) and STM results show a bulk-terminated (1 × 1) surface, which is supported by first-principles density functional theory (DFT) calculations. Atomically resolved STM images are consistent with Tersoff–Hamann calculations that show that surface In atoms are imaged bright or dark, depending on the configuration of their O neighbors. The coordination of surface atoms on the In2O3(111)–1×1 surface is analyzed in terms of their possible role in surface chemical reactions.

Effects of synthesis parameters on the microstructure and phase structure of porous 316L stainless steel supported TiO 2 membranes

Porous stainless steel (PSS) supported TiO 2 membrane was synthesized from colloidal TiO 2 sol by the sol–gel technique. Morphology and phase structure of the obtained membranes were regulated through optimizing the synthesis parameters including organic binders, aging periods of the parent sol and concentrations of the casting solutions as well as the sintering temperatures. Polyvinyl alcohol (PVA) 1750 was found to be feasible to fabricate TiO 2 membrane with relatively flat surface and homogeneous morphology without crack. The aging period of the parent sol, which was revealed to be very important to the morphology of the particles deposited in the membranes on PSS, was decided to be 24 h. The concentration, under which the membranes could avoid macro-pores and have a uniform thickness of approximately 8 μm, was regulated to 0.0036 mol/l. Besides, a homogeneous microstructure with grain sizes of 0.08–0.2 μm was obtained in the membrane with a pure rutile phase when sintered at 850 °C. The obtained PSS supported TiO 2 membrane with homogeneous microstructure and rutile phase may be very promising for practical applications.

Buckling Stabilization and Stress Reduction in SiC on Si by i-FLASiC Processing

One of the main challenging tasks in the prospective technology is the buckling suppression of the 3C-SiC film due to the melting and solidification process and the stress relief as a consequence of the short time Si melting during the Flash Lamp Annealing. To overcome this effect and to stabilize a flat surface morphology an alternative i-FlASiC process was developed. This work refers to the influence of the layer stack modifications by doping and meltstop formation by ion implantation on the wafer buckling. The samples were studied by transmission electron microscopy, high resolution x-ray diffraction and infrared ellipsometry. The aim was to optimize the doping and flash lamp annealing conditions in relation to the i-FLASiC layer stack modification.

Wet cleaning and surface characterization of Si 1− xGe x virtual substrates after a CMP step

New reactants such as ozone dissolved in ultra-pure water have been widely used the last few years instead of the original Radio Corporation of America (RCA) cleaning (which is a combination of the Standard Cleaning 1 (SC1) and the Standard Cleaning 2 (SC2)). In a first part of the study (Microelectron. Eng. 83 (2006) 1986), we had quantified the efficiency of a new cleaning sequence (that calls upon HF and H 2O/O 3 solutions) on polished Si 1− x Ge x virtual substrates ( x = 0.2–0.5). We are discussing here the surface morphology and wetability together with the oxide thickness and structure typically obtained after this so-called “DDC-SiGe” wet cleaning. Flat surface morphologies are found after cleaning whatever the Ge content (from 20 to 50%). Typical root mean square roughness is around 0.4 nm. We have used X-ray Photoelectron Spectroscopy to determine the characteristics of the surface termination after this “DDC-SiGe” cleaning. An oxide mainly composed of SiO 2 is formed, with a low fraction of Ge sub-oxide and GeO 2. The distribution of chemical species is not that different from the one obtained after the use of a SC1 cleaning. However, the chemical oxide formed is slightly thicker. Such a HF/O 3 cleaning leads, when used on thick Ge layers grown on Si, to the formation of a really thin Ge sub-oxide. Our oxidation model assumes a competition in O 3 solutions between the oxidation rates of Si and Ge atoms (faster for Si) and the dissolution of the Ge oxide formed in solution. This mechanism, which implies the formation of a slightly porous oxide, is different from the one seeming to occur in SC1-based solutions. Indeed, the addition of surfactant in a SC1 solution modifies the oxidation rate compared to standard SC1 or O 3-based solutions, suggesting a diffusion of reactants towards the interface between the SiGe and the oxide in formation, assisted by the reactions of species within the cleaning solutions.

Epitaxial Growth of (0001)Ru Thin Films on (111)ZrN/(111)Si by Low-Temperature Process and Their Surface Morphologies

We have investigated the epitaxial growth of (0001)Ru thin films on (111)ZrN/(111)Si epitaxial systems at room temperature using an ultrahigh-vacuum dc magnetron sputtering system. The film quality obtained and the epitaxial relationship were evaluated by X-ray diffraction, X-ray pole figure, grazing-incidence-angle X-ray reflectivity, and atomic force microscopy analyses. It was found that (0001)Ru films with a thickness of 100 nm were grown epitaxially on a (111)ZrN(40 nm)/(111)Si system even at room temperature with the directional relationship of Ru(0001)[1120]∥ZrN(111)[110]∥Si(111)[110]. In addition, it was also clarified that an epitaxial (0001)Ru film with a thickness of 3 nm on a (111)ZrN (6 nm)/(111)Si system can be regarded as a dense film with the same density as the bulk, and exhibits a fairly flat surface morphology with an average surface roughness of approximately 0.2–0.3 nm.