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In modern biomaterial-based electronics, conductive and flexible biomaterials are gaining increasing attention for their wide range of applications in biomedical and wearable electronics industries. The ecofriendly, biodegradable, and self-resorbable nature of these materials makes them an excellent choice in fabricating green and transient electronics. Surface functionalization of these biomaterials is required to cater to the need of designing electronics based on these substrate materials. In this work, a low-temperature atomic layer deposition (ALD) process of platinum (Pt) is presented to deposit a conductive thin film on collagen biomaterials, for the first time. Surface characterization revealed that a very thin ALD-deposited seed layer of TiO2on the collagen surface prior to Pt deposition is an alternative for achieving a better nucleation and 100% surface coverage of ultrathin Pt on collagen surfaces. The presence of a pure metallic Pt thin film was confirmed from surface chemical characterization. Electrical characterization proved the existence of a continuous and conductive Pt thin film (∼27.8 ± 1.4 nm) on collagen with a resistivity of 295 ± 30 μΩ cm, which occurred because of the virtue of TiO2. Analysis of its electronic structures showed that the presence of metastable state due to the presence of TiO2enables electrons to easily flow from valence into conductive bands. As a result, this turned collagen into a flexible conductive biomaterial.

Surface modifications of a biomaterial like collagen are crucial in improving the surface properties and thus enhancing the functionality and performance of such a material for a variety of biomedical applications. In this study, a commercially available collagen membrane’s surface was functionalized by depositing an ultrathin film of titania or titanium dioxide (TiO2) using a room temperature atomic layer deposition (ALD) process. A novel titanium precursor–oxidizer combination was used for this process in a custom-made ALD reactor. Surface characterizations revealed successful deposition of uniform, conformal TiO2thin film on the collagen fibrillar surface, and consequently, the fibers became thicker making the membrane pores smaller. The in vitro bioactivity of the ALD-TiO2thin film coated collagen was investigated for the first time using cell proliferation and a calcium phosphate mineralization assay. The TiO2-coated collagen demonstrated improved biocompatibility promoting higher growth and proliferation of human osteoblastic and mesenchymal stem cells when compared to that of noncoated collagen. A higher level of calcium phosphate or apatite formation was observed on ALD modified collagen surface as compared to that on noncoated collagen. Therefore, this novel material can be promising in bone tissue engineering applications.

Nickel yttria-stabilized zirconia (Ni-YSZ) is used as anode material for solid oxide fuel cells (SOFCs). The electrochemical performance of Ni-YSZ anodes can be improved when the size of constituent particles of nickel is reduced. However, at SOFC high temperature operating environments, nano-sized Ni particles suffer from sintering. Nanoscale Ni-YSZ anodes can undergo severe structure changes. In this work, a unique approach of fabricating a nanostructured Ni-YSZ anode is demonstrated by combining atomic layer deposition (ALD) and glancing angle deposition (GLAD) techniques whereby nickel nanoparticle sintering is prevented at high temperatures with as thin as 1.9 nm YSZ ALD coating on the nickel; the surface area of the resulting Ni-YSZ anode was found to increase more than 3 times that of a planar electrode. In addition, the novel ALD/GLAD coating approach used here provides an ionic conductive YSZ electrolyte phase combined with an electrical conductive Ni phase whereby porosity can be controlled through deposition and post-deposition annealing. In addition, the surface roughness of Ni-YSZ anode decreases with increasing YSZ coating layer thickness and it is unaffected by the post-deposition annealing process. Conductivity measurements of the Ni-YSZ anodes at room temperature show a resistivity in the order of 10[?]4 cm*S[?]1.

Use of common atomic layer deposition (ALD) oxygen sources such as oxygen, ozone or water often causes uncontrolled oxidation of the silicon surface by diffusion through the growing HfO2 film during the ALD process. This results in thick interfacial layer (IL) that is detrimental to future transistor scaling if further thinning of the IL is desired. In order to minimize the uncontrolled oxidation at the interface, we explored the use of ethanol as the ALD oxygen source in the ALD HfO2 process. The effect of using ethanol on the growth, composition and electrical behavior of ALD HfO2 films was studied and compared against films prepared using water based ALD process. Ethanol showed good reactivity with the hafnium precursor tetrakis(diethylamino)hafnium and displayed typical ALD growth behavior of linear film growth within a wide ALD process temperature window (200-280 degC). The ethanol based ALD process exhibited HfO2 growth rate of 0.05 nm/cycle which was less than 0.15 nm/cycle obtained when water was used as the ALD oxygen source. X-ray photoelectron spectroscopy (XPS) showed the deposition of stoichiometric HfO2 with trace amount of carbon in the film. SiO2 interfacial layer was not observed in as-deposited samples, whereas annealed samples showed SiO2 XPS features. Films prepared using the ethanol based ALD process showed comparable dielectric performance to that of water based ALD process films and displayed well behaved C-V and I-V curves with as-deposited (ethanol) HfO2 samples showing the lowest leakage current density of 5 x 10-8 A/cm2 at 1 V gate bias.

A novel atomic layer deposition (ALD) route of Y2O3 thin films was developed and demonstrated utilizing Y(iPrCp)3 and O3. The ALD growth characteristics were investigated by varying precursor dosage, reactor temperature, and number of deposition cycles. The growth rate of Y2O3 was found to be 0.17 {plus minus} 0.01 nm/cycle within the ALD temperature window of 245 - 300 oC. The resulting films were analyzed with spectral ellipsometry and x-ray photoelectron spectroscopy, in order to determine stoichiometry, impurity, annealing behavior, and refractive index. The results of this work demonstrate the potential for suggesting Y(iPrCp)3 as a suitable ALD precursor and Ar+ beam as an effective means of removing surface Y(OH)3 on Y2O3 films.

Er1-xTixOy dielectric thin films were deposited on Si(100) substrates by atomic layer deposition (ALD) using tris(methylcyclopentadienyl)erbium [(CpMe)3Er] and tetrakis(diethylamino)titanium [TDEAT] as metal precursors, and O3 as oxidant. The deposition temperature dependence of both Er2O3 and TiO2 film growths showed the overlapping ALD window of 175-250degC. Compositional tunability of Er1-xTixOy films was obtained through deposition process control. Carbon and nitrogen impurities in as-deposited films were found to be below X-ray photoelectron spectroscopy detection level. Glancing incidence X-ray diffraction and phase-shifting interferometry results showed that ErxTi1-xOy films with ALD cycle ratios (Er2O3/TiO2) of 1:8 or higher have a good thermal stability and remain amorphous with unchanged surface roughness after post-deposition rapid thermal processing (RTP) at 700degC in O2. Electrical measurements showed that optimized amorphous Er1-xTixOy films after RTP exhibited a dielectric constant of [?]36, a hysteresis voltage of less than 10 mV, and a leakage current density of 10[?]8 A/cm2 at [?]1 MV/cm; such properties compare favorably with the properties of other reported amorphous titanium-based ternary dielectrics on Si. The sizable reduction of leakage current density of Er1-xTixOy found in our study suggests that amorphous Er1-xTixOy thin films are promising future dielectrics in Si integrated circuit technology.

Diethylzinc precursor and hydrogen sulfide were used for the atomic layer deposition (ALD) of ZnS films on thioacetamide (TAM)-treated p-type GaSb substrates for the passivation of GaSb-based devices. The film growth rate was found to be 0.13+-0.01 nm/cycle with an ALD window of 175 - 275 degC. X-ray photoelectron spectroscopy (XPS) analyses of as-deposited ZnS films showed that the resulting films were stoichiometric ZnS with no evidence of other sulfur species in the film. XPS indicated the surface of GaSb treated with TAM was a mixture of Ga-S and Sb-S without detectable oxides. After the ALD of 1 nm-thick ZnS on TAM-treated GaSb, the major component at the interface of ZnS/TAM-treated GaSb system was found to be gallium sulfide. Surface morphology and structure of as-deposited ZnS were studied with phase-shifting interferometry and grazing incidence X-ray diffraction.

Tetrakis (diethylamino) hafnium (TDEAH), tetrakis (diethylamino) titanium (TDEAT), and were used for the atomic layer deposition (ALD) of , , and films on silicon substrates. The ALD temperature windows were found to be for and for . The overlap region is ideal for the ALD of the films. Different compositions of were obtained by varying the cycle ratios, and excellent tunability of film composition was found using X-ray photoelectron spectroscopy (XPS). The deposition rate was found to be the superposition of the two individual growth rates. Both as-deposited and postdeposition annealed films were studied with XPS, phase shift interferometry, and grazing incidence X-ray diffraction. As-deposited and films were found to be amorphous, and they began to crystallize after annealing at in the monoclinic phase and in weak anatase phase . The films remained amorphous after annealing up to about in for .

Differences in the magnitude of cerebrospinal fluid (CSF) volumetric flow through the cerebral aqueduct between healthy and hydrocephalic patients have been previously reported. However it is not clear whether this is directly related to the pathophysiology or secondary to altered ventricular morphology and hydrodynamics. This work aims to determine the role of anatomic and hydrodynamic factors in modulating the magnitude of CSF flow through the aqueduct.

Lyapunov-Schmidt reduction and singularity theory analytical techniques are used to study degenerate Hopf bifurcations in a single-species, gas-solid catalytic reaction system. The reactor is assumed to be well mixed and isothermal. The inlet pressure of the reactant is used as a bifurcation parameter. Adsorbate-adsorbate interactions are quantified by a linear increase in activation energy for desorption with coverage. The surface reaction is assumed to require a single site. In spite of the apparent simplicity of the model, the analysis reveals a structure rich in dynamic behavior patterns. The strengths and weaknesses of the analytical methods are discussed in view of the results obtained.

The influences of surface speciation upon the catalytic oxidation kinetics of methanol on palladium under ambient-pressure flow-reactor conditions was examined by surface-enhanced Raman spectroscopy (SERS) combined with mass spectrometry (MS) and compared with corresponding data on rhodium. The former technique provides uniquely sensitive surface vibrational information under real-time (≈1 s)in situconditions, by utilizing ultrathin catalyst films electrodeposited onto an inert SERS-active gold substrate. These transition-metal surfaces exhibit sufficiently robust SERS activity to enable temperature-dependent spectral measurements over the range 25–500°C. Parallel kinetic measurements undertaken with MS show the occurrence of methanol decomposition (to CO and H2) in the absence of O2on both Pd and Rh. While the presence of a molar deficiency of O2yields methanol oxidation (to form CO2and H2) in addition to methanol decomposition on Rh, only the latter occurred (at slower rates than Rh) on Pd. These dissimilar reaction selectivities are consistent with the absence of surface vibrational features on the latter surface and the observed presence of adsorbed CO on the former. The behavior can be rationalized by the paucity of adsorbed atomic oxygen, O(ad), on Pd compared with Rh arising from the greater ability of the latter to dissociatively chemisorb O2. Both catalysts induced exhaustive methanol oxidation (yielding CO2and H2O) in a heavily O2-rich reactant mixture, although Pd again yielded less facile reaction kinetics. In addition, a significant catalyst deactivation occurred upon heating Pd in this reactant mixture, which was entirely absent on Rh. The corresponding temperature-dependent SER spectra indicate the formation of palladium oxide (PdO) by 350°C, which was retained entirely upon subsequent cooling. While an oxide (Rh2O3) was also seen by SERS to form on Rh by 350°C under these conditions, this species was removed upon subsequent cooling. Transient SERS measurements following sudden exposure of such oxidized surfaces to a methanol gas stream revealed that PdO was entirely unreactive toward methanol even at 350°C, while, in contrast, Rh2O3was removed entirely within ca. 5 s. This remarkable difference in oxide reactivity, which accounts for the Pd catalyst deactivation, was deduced to be due primarily to the inability of methanol to yield a suitable adsorbed “oxygen scavenger” by dissociative chemisorption on Pd. The possible involvement of a methoxy intermediate in the reaction on Pd under O2-rich conditions, as suggested by the SERS data, is also discussed.

Application of forced oscillations to chemical reactor systems is investigated for three systems based on: (1)a homogeneous/heterogeneous reaction mechanism proposed by Horn and Bailey (1968) (2)amine and alcohol reactions on oxide catalysts and (3)cobalt catalyzed CO methanation. Previous analyses of these systems have demonstrated experimentally and/or theoretically, significant enhancements in reactor performance upon periodic operation. For the three cases investigated, computer-simulated modelling confirms great improvements in reactor performance upon periodic concentration forcing: (1)30% enhancement in selectivity, (2)50 fold increase in reaction rate and (3)13 fold improvement in conversion, respectively. However, it is also observed that yield improvements in these systems do not exceed or even match the performance obtained under optimal steady state conditions.

Surface-enhanced Raman spectroscopy (SERS), combined with simultaneous mass spectrometric measurements, has been utilized to probe the reactive nature of surface species present during the reduction of NO by CO on Pt and Pd. As in our earlier studies, the SERS-active transition-metal surfaces are prepared by electrodepositing ultrathin films onto electrochemically roughened gold. These surfaces display remarkably robust SERS activity, enabling intense Raman spectra to be obtained over a range of reactant pressures (here up to 1 atm) and at temperatures up to at least 400°C. During nitric oxide adsorption at 1 atm on Pt, both terminal (240 and 470 cm−1) and bridged (325 cm−1) states of molecular NO were detected at lower temperatures (25–200°C), with some dissociation occurring at higher (ca 250°C) temperatures as evidenced by the presence of atomic nitrogen (295 cm−1). Similarly, a bridged NO species (310 cm−1) was observed on Pd under similar conditions, with dissociation detected in the form of atomic nitrogen (285 cm−1) and surface oxide (450 and 665 cm−1). Co-dosing of reactants on platinum produced a surface dominated by NO and CO (470 and 2080 cm−1), whereas the former was adsorbed preferentially on Pd. Simultaneous SERS/MS measurements were performed during reaction of an equimolar reactant mixture at 1 atm of total pressure over both metals. Both CO2and N2O were formed during reaction on Pt, with onset of detectable product formation correlating with depletion of adsorbed CO and NO, respectively. In contrast, CO2was the only product detected over Pd, with the depletion of surface oxygen suggesting that NO dissociation may be rate limiting at higher temperatures (ca 300°C). The extent of dissociation on these surfaces is compared and contrasted, with particular emphasis placed on its role in determining reaction selectivity. Furthermore, the overall behavior of these catalysts is compared with our former observations regarding this reduction process on rhodium.

Surface-enhanced Raman spectroscopy (SERS) combined with X-ray photoelectron spectroscopy (XPS) has been utilized to study the oxidation of ruthenium at ambient pressure (1 atm) and elevated temperatures (25–300°C). The SERS probe providesin-situvibrational information regarding surface oxide bonding. While the XPS probe necessarily involvesex-situmeasurements (i.e., transfer to and from ultrahigh vacuum), it provides valuable complementary information on the metal and oxygen electronic states. Ruthenium surfaces were prepared by electrodepositing ultrathin films (about three monolayers) onto electrochemically roughened (i.e., SERS-active) gold substrates. Insight into thein-situoxidation process was obtained by probing the changes of surface speciation by SERS upon heating Ru in flowing O2. A pair of SERS bands at 470 and 670 cm−1appear in the spectrum acquired for a freshly electrodeposited film, which are assigned to different stretching modes of hydrated RuO2formed during sample transfer to the gas-phase reactor. However, a fully reduced Ru surface (i.e., devoid of oxide features) could be formed by adsorbing a protective CO adlayer in an electrochemical cell followed by heating to 200°C in vacuum so to thermally desorb the CO. While the initially oxidized (i.e., RuO2) surface was stable to further oxidation upon heating in O2, adsorbed atomic oxygen was detected at 200°C from the appearance of a SERS band at 600 cm−1and a XPS O(1s) peak at 531.7 eV. In contrast, the higher oxides RuO4and possibly RuO3were produced only upon thermal oxidation of the fully reduced Ru surface. Evidence for RuO3formation includes the appearance of a 800 cm−1SERS band at 200°C which correlates with the advent of a Ru(3d5/2) peak at 282.6 eV. The surface was further oxidized to RuO4at 250°C, as deduced from the formation of a 875 cm−1band and a Ru(3d5/2) peak at 283.3 eV. While RuO3and RuO4were exclusively formed at temperatures higher than 250°C, RuO2was produced upon cooling to room temperature, possibly via the decomposition of RuO4.

Trying to identify the mechanism(s) responsible for isothermal oscillatory behavior of heterogeneous catalytic reaction systems, many investigators have assumed low conversions with respect to the limiting reactant(s) so that the bulk phase concentrations of the reactants may be considered constant. In this study, it is shown that even in a differential catalytic CSTR, in which conversion of the reactants may be less than %, the changes of the gas phase concentrations of the reacting.species may play a key role in the overall dynamic behavior of a reaction system; for instance, they may drive the oscillations observed. The reduction of nitric oxide by ammonia on polycrystalline platinum is discussed in detail within this context. Several other oxidation reactions are also discussed

The presence or absence of copper surface oxidation in air is shown to be readily controllable by aqueous solution rinsing. The presence of a film is detected from the oxide vibrational features obtained by surface-enhanced Raman scattering. Flushing with acidic solutions removes the film to yield a reduced surface, whereas rinsing with aerated neutral or alkaline media immediately regenerates the oxide. The findings are entirely compatible with the occurrence of electrochemical half-reaction pathways for surface oxidation and reduction. (c)1999 The Electrochemical Society

Nickel yttria-stabilized zirconia (Ni-YSZ) is used as anode material for solid oxide fuel cells (SOFCs). The electrochemical performance of Ni-YSZ anodes can be improved when the size of constituent particles of nickel is reduced. However, at SOFC high temperature operating environments, nano-sized Ni particles suffer from sintering. Nanoscale Ni-YSZ anodes can undergo severe structure changes. In this work, a unique approach of fabricating a nanostructured Ni-YSZ anode is demonstrated by combining atomic layer deposition (ALD) and glancing angle deposition (GLAD) techniques whereby nickel nanoparticle sintering is prevented at high temperatures with as thin as 1.9 nm YSZ ALD coating on the nickel; the surface area of the resulting Ni-YSZ anode was found to increase more than 3 times that of a planar electrode. In addition, the novel ALD/GLAD coating approach used here provides an ionic conductive YSZ electrolyte phase combined with an electrical conductive Ni phase whereby porosity can be controlled through deposition and post-deposition annealing. In addition, the surface roughness of Ni-YSZ anode decreases with increasing YSZ coating layer thickness and it is unaffected by the post-deposition annealing process. Conductivity measurements of the Ni-YSZ anodes at room temperature show a resistivity in the order of 10−4cm·S−1.

Use of common atomic layer deposition (ALD) oxygen sources such as oxygen, ozone or water often causes uncontrolled oxidation of the silicon surface by diffusion through the growing HfO2film during the ALD process. This results in thick interfacial layer (IL) that is detrimental to future transistor scaling if further thinning of the IL is desired. In order to minimize the uncontrolled oxidation at the interface, we explored the use of ethanol as the ALD oxygen source in the ALD HfO2process. The effect of using ethanol on the growth, composition and electrical behavior of ALD HfO2films was studied and compared against films prepared using water based ALD process. Ethanol showed good reactivity with the hafnium precursor tetrakis(diethylamino)hafnium and displayed typical ALD growth behavior of linear film growth within a wide ALD process temperature window (200-280 °C). The ethanol based ALD process exhibited HfO2growth rate of 0.05 nm/cycle which was less than 0.15 nm/cycle obtained when water was used as the ALD oxygen source. X-ray photoelectron spectroscopy (XPS) showed the deposition of stoichiometric HfO2with trace amount of carbon in the film. SiO2interfacial layer was not observed in as-deposited samples, whereas annealed samples showed SiO2XPS features. Films prepared using the ethanol based ALD process showed comparable dielectric performance to that of water based ALD process films and displayed well behaved C-V and I-V curves with as-deposited (ethanol) HfO2samples showing the lowest leakage current density of 5 x 10-8A/cm2at 1 V gate bias.

A novel atomic layer deposition (ALD) route of Y2O3 thin films was developed and demonstrated utilizing Y(iPrCp)3 and O3. The ALD growth characteristics were investigated by varying precursor dosage, reactor temperature, and number of deposition cycles. The growth rate of Y2O3 was found to be 0.17 {plus minus} 0.01 nm/cycle within the ALD temperature window of 245 - 300 ºC. The resulting films were analyzed with spectral ellipsometry and x-ray photoelectron spectroscopy, in order to determine stoichiometry, impurity, annealing behavior, and refractive index. The results of this work demonstrate the potential for suggesting Y(iPrCp)3 as a suitable ALD precursor and Ar+ beam as an effective means of removing surface Y(OH)3 on Y2O3 films.

Er1-xTixOydielectric thin films were deposited on Si(100) substrates by atomic layer deposition (ALD) using tris(methylcyclopentadienyl)erbium [(CpMe)3Er] and tetrakis(diethylamino)titanium [TDEAT] as metal precursors, and O3as oxidant. The deposition temperature dependence of both Er2O3and TiO2film growths showed the overlapping ALD window of 175–250°C. Compositional tunability of Er1-xTixOyfilms was obtained through deposition process control. Carbon and nitrogen impurities in as-deposited films were found to be below X-ray photoelectron spectroscopy detection level. Glancing incidence X-ray diffraction and phase-shifting interferometry results showed that ErxTi1-xOyfilms with ALD cycle ratios (Er2O3/TiO2) of 1:8 or higher have a good thermal stability and remain amorphous with unchanged surface roughness after post-deposition rapid thermal processing (RTP) at 700°C in O2. Electrical measurements showed that optimized amorphous Er1-xTixOyfilms after RTP exhibited a dielectric constant of ∼36, a hysteresis voltage of less than 10 mV, and a leakage current density of 10−8A/cm2at −1 MV/cm; such properties compare favorably with the properties of other reported amorphous titanium-based ternary dielectrics on Si. The sizable reduction of leakage current density of Er1-xTixOyfound in our study suggests that amorphous Er1-xTixOythin films are promising future dielectrics in Si integrated circuit technology.

Diethylzinc precursor and hydrogen sulfide were used for the atomic layer deposition (ALD) of ZnS films on thioacetamide (TAM)-treated p-type GaSb substrates for the passivation of GaSb-based devices. The film growth rate was found to be 0.13±0.01 nm/cycle with an ALD window of 175 - 275 °C. X-ray photoelectron spectroscopy (XPS) analyses of as-deposited ZnS films showed that the resulting films were stoichiometric ZnS with no evidence of other sulfur species in the film. XPS indicated the surface of GaSb treated with TAM was a mixture of Ga-S and Sb-S without detectable oxides. After the ALD of 1 nm-thick ZnS on TAM-treated GaSb, the major component at the interface of ZnS/TAM-treated GaSb system was found to be gallium sulfide. Surface morphology and structure of as-deposited ZnS were studied with phase-shifting interferometry and grazing incidence X-ray diffraction.

A pH adjusted acidic solution of thioacetamide (TAM) was used as a sulfidizing agent to treat long wavelength infrared (LWIR) superlattice surface for the first time. The results were compared against those for ammonium sulfide [(NH4)2S] which have been used earlier for the same purpose. X-ray photoelectron spectroscopy (XPS) results revealed that TAM treatment attains a much pronounced degree of sulfidization on superlattice surface. Electrical measurements on mesa-etched diodes exhibited maximum zero bias dynamic resistance times area (R0A) value of 590 -cm2, approximately a four times improvement compared to (NH4)2S treated diodes. XPS studies revealed the reappearance of detrimental oxides on the TAM treated surface after long term air exposure asserting the need for a suitable capping layer to preserve the quality of the surface. Atomic layer deposition (ALD) was used to cap the TAM treated surface with zinc sulfide (ZnS). Precise deposition of few monolayers of ZnS on TAM treated surface was further studied using XPS to understand the evolution of bond formations at the semiconductor-dielectric interface.

Tetrakis (diethylamino) hafnium (TDEAH), tetrakis (diethylamino) titanium (TDEAT), and H2Owere used for the atomic layer deposition (ALD) of HfO2, TiO2, and HfxTi1−xO2films on silicon substrates. The ALD temperature windows were found to be 175–250°Cfor HfO2(0.12nm∕cycle)and 150–250°Cfor TiO2(∼0.06nm∕cycle). The 175–250°Coverlap region is ideal for the ALD of the HfxTi1−xO2films. Different compositions of HfxTi1−xO2were obtained by varying the [TDEAH∕H2O]∕[TDEAT∕H2O]cycle ratios, and excellent tunability of film composition was found using X-ray photoelectron spectroscopy (XPS). The HfxTi1−xO2deposition rate was found to be the superposition of the two individual growth rates. Both as-deposited and postdeposition annealed films were studied with XPS, phase shift interferometry, and grazing incidence X-ray diffraction. As-deposited HfO2and TiO2films were found to be amorphous, and they began to crystallize after annealing at 600°Cin the monoclinic phase (HfO2)and in weak anatase phase (TiO2). The HfxTi1−xO2films remained amorphous after annealing up to about 1000°Cin N2for 5min.

α-Fe2O3thin films have been deposited on Si(100) substrates using n-butylferrocene and oxygen in a low-pressure metallorganic chemical vapor deposition reactor. The iron precursor is liquid at room temperature having a high enough vapor pressure; its thermogravimetric analysis shows that it undergoes clean evaporation without decomposition. The growth rates were studied in the temperature range of 400–600°C. The resulting thin films were characterized for structure and morphology using X-ray diffraction and scanning electron microscopy. Their composition was analyzed using energy-dispersive X-ray spectroscopy, and chemical bonding states were probed using X-ray photoelectron spectroscopy. Films deposited at 450°Cwere mostly noncrystalline and had carbon contamination. Films deposited at higher temperatures were crystalline α-Fe2O3.

Titanium aluminum oxide films have been studied as potential alternative gate dielectrics. However, most studies have focused on sputtered films. In this study, we demonstrate that a combination of tetrakis(diethylamino)titanium, trimethyl aluminum, oxygen, and cyclic chemical vapor deposition (CVD) is a promising approach for laminated TiO2∕Al2O3films with low impurities and high thermal stability even at low temperatures. The growth of the films is carried out in a cold-wall CVD chamber at 300°Cand 0.7Torr. Our studies show that the properties of TiO2improve with the addition of even a few percent of Al2O3. X-ray diffraction analyses indicate that as-deposited TiO2∕Al2O3films have amorphous structure. Upon annealing as-deposited films in Ar at 700°Cfor 5min, TiO2∕Al2O3films maintain their amorphous structure, while pure TiO2films crystallize at these conditions. Atomic force microscopy shows that the surfaces of TiO2∕Al2O3films are smoother than those of TiO2films deposited at the same conditions. Even though annealing increases the roughness of the TiO2∕Al2O3films, film roughness is still significantly lower than that of as-deposited TiO2films. Moreover, Rutherford backscattering spectroscopy and X-ray photoelectron spectroscopy show that there is no detectable formation of interfacial silicon oxide and negligible carbon impurity in as-deposited TiO2∕Al2O3films.