Room Temperature Atomic Layer Deposition Research Articles

Room temperature atomic layer deposition of zinc titanium oxide using sequential adsorption of dimethyl zinc and tetrakis(dimethylamino)titanium

Complex oxide films of TiO2 and ZnO are deposited by RT atomic layer deposition (ALD) with a sequential adsorption process. In this ALD, a Zn precursor of dimethyl zinc (DMZ) and a Ti precursor of tetrakis(dimethylamino)titanium (TDMAT) are used. In the sequential adsorption step, the DMZ saturation on the surface is followed by partial adsorption of TDMAT. It is assumed that the TDMAT molecule is adsorbed on the DMZ uncovered area. The mixed layer of DMZ and TDMAT is formed in the adsorption step, followed by being oxidized with the plasma-excited humidified Ar. All the ALD processes are performed at RT without any sample heating in the ALD chamber. The growth per cycle of the balanced Zn and Ti oxide deposition is recorded at 0.086 nm/cycle. The mixing ratio of Zn and Ti is controlled by the TDMAT exposure in the adsorption step. In this study, the reaction model and the related rate equations to calculate the mixing concentration ratio are proposed based on the in situ observation of the surface reaction by IR absorption spectroscopy.

Collagen membrane functionalized with magnesium oxide via room-temperature atomic layer deposition promotes osteopromotive and antimicrobial properties.

Artificial bone grafting materials such as collagen are gaining interest due to the ease of production and implantation. However, collagen must be supplemented with additional coating materials for improved osteointegration. Here, we report room-temperature atomic layer deposition (ALD) of MgO, a novel method to coat collagen membranes with MgO. Characterization techniques such as X-ray photoelectron spectroscopy, Raman spectroscopy, and electron beam dispersion mapping confirm the chemical nature of the film. Scanning electron and atomic force microscopies show the surface topography and morphology of the collagen fibers were not altered during the ALD of MgO. Slow release of magnesium ions promotes bone growth, and we show the deposited MgO film leaches trace amounts of Mg when incubated in phosphate-buffered saline at 37°C. The coated collagen membrane had a superhydrophilic surface immediately after the deposition of MgO. The film was not toxic to human cells and demonstrated antibacterial properties against bacterial biofilms. Furthermore, in vivo studies performed on calvaria rats showed MgO-coated membranes (200 and 500 ALD) elicit a higher inflammatory response, leading to an increase in angiogenesis and a greater bone formation, mainly for Col-MgO500, compared to uncoated collagen. Based on the characterization of the MgO film and in vitro and in vivo data, the MgO-coated collagen membranes are excellent candidates for guided bone regeneration.

Reliability Enhancement of 14 nm HPC ASIC Using Al2O3 Thin Film Coated with Room-Temperature Atomic Layer Deposition

In this research, a 14 nm high-performance computing application-specific integrated circuit was coated with a 5–20 nm Al2O3 thin film by atomic layer deposition in room-temperature conditions to study its performance in terms of reliability with different thicknesses. An open/short test, standby current measurement, interface input/output performance test, and phase-locked loops functional test were used to verify chip performance. Furthermore, an unbiased highly accelerated temperature and humidity stress test and a 72 h wear-out test were used to study the effects of the atomic layer deposition coating. The results showed that the coating thickness of 15 nm provided the best performance in the wear-out test, as well as the unbiased highly accelerated temperature humidity stress. This study demonstrates that room-temperature atomic layer deposition is a promising technique for enhancing the reliability of advanced node semiconductor chips.

Room-temperature atomic layer deposition of SiO2 on microcracked ZrO2 layers

Yttria-stabilized zirconia (Y-SZ) has become a reliable material option to restore severely compromised teeth. Y-SZ materials are prone to low-temperature degradation (LTD), which generates a tetragonal-to-monoclinic (t-m) transformed, porous layer. We suggest that room-temperature atomic layer deposition (RT-ALD) could be used for the infiltration and deposition of nanoscale SiO2 film over this layer, creating a protective hybrid surface against further degradation by LTD. This study investigated the potential of developing a Y-SZ transformed layer under controlled conditions for the infiltration of silica using RT-ALD, aiming to develop a hybrid zirconia-silica interface, and to investigate the effect of silica deposition/infiltration via RT-ALD on the surface roughness and wettability of zirconia-based materials. Sintered specimens (14 mm × 4 mm x 2 mm) were prepared from four different Y-SZ materials (n = 40): low translucency 3 mol % Y-SZ (3Y-LT; Ceramill ZI, Amann Girrbach); high translucency 4 mol % Y-SZ (4Y-HT; Ceramill Zolid); and two high translucency 5 mol % Y-SZ (5Y-HT – Lava Esthetic, 3M; 5Y-SHT – Ceramill Zolid, FX white). Specimens were exposed to hydrothermal treatment (HTT) to develop similar depths of crystalline changes. RT-ALD was used to deposit a thin film of silica (SiO2). Surface roughness and wettability analyses were performed to investigate the effect of treatment (HTT and RT-ALD) and material on Y-SZ surface properties, and data was analyzed by two-way ANOVA and Tukey HSD (p < 0.05). RT-ALD and HTT-RT-ALD treated specimens of 3Y-LT and 5Y-HT materials were exposed to further hydrothermal aging (HA) and the surface was characterized by time-of-flight secondary ion mass spectrometry (ToF-SIMS). There was a significant interaction effect of material and treatment (HTT and RT-ALD) on roughness (p = 0.02), and surface wettability (p < 0.001). Silica deposition via RT-ALD resulted in a significant increase in surface roughness of all materials tested, while surface wettability was either improved or not changed based on the material type and HTT exposure. Nanofilms of SiO2 were successfully deposited on Y-SZ materials and infiltrated 3Y-LT zirconia.

Multiple layers of aluminum silicate and silicon dioxide deposited by room-temperature atomic layer deposition for enhanced cation sorption

Multiple layers of aluminum silicate and SiO2 are deposited at room temperature (RT) by repeating a combination of aluminum-silicate atomic layer deposition (ALD) and a plural number of SiO2 ALDs. The RT-ALD is performed by using precursors of tris(dimethylamino)silane and trimethyl aluminum (TMA). The oxidizing gas is plasma excited humidified Ar. A cross-sectional transmission electron microscope and angle resolved x-ray photoelectron spectroscopy suggest that aluminum from the TMA molecule is diffused to SiO2 to form an aluminum silicate layer with the Al rich surface at RT. The deposited film shows an enhanced Na sorption in an NaCl aqueous solution of 10 mM, compared with the pure aluminum silicate layer without the SiO2 layer. It is assumed that the bond formation of Al–O–Al in the aluminum silicate film is suppressed by limiting the thickness of the aluminum silicate layer. Multiple films are also applicable for Cs and K ion sorption. The effects of the multiple layers on the ion sorptivity are discussed in the paper.

Silica deposition on zirconia via Room-Temperature Atomic Layer Deposition and bond strength to resin-based luting agent

To evaluate the effect of the controlled growth of yttria-stabilized zirconia (Y-PSZ) transformed layer and silica deposition via Room-Temperature Atomic Layer Deposition (RT-ALD) on the shear bond strength (SBS) between Y-PSZ and luting agent. Y-PSZ specimens (IPS e.max ZirCAD) with different translucencies (MO, MT, LT) were exposed to surface treatments (n = 10): control (C - no treatment), aged (A - 15 h, 134 °C, 2 bar in autoclave), blasted (B - 50 μm Al2O3), silica deposition via RT-ALD (R - 40 cycles of sequential exposure to tetramethoxysilane orthosilicate and ammonium hydroxide vapors) and aged followed by silica deposition (AR). Specimens were bonded to resin composite cylinders with a luting agent (Multilink Automix) and SBS test was performed. Failure mode and surface chemical and topographical characterization (energy-dispersive spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy) were performed. SBS data was analyzed by two-way ANOVA and Tukey test (α = 0.05). Silica deposition resulted in SBS values similar to alumina blasting (p > .848), with no significant effect of aging (p > .664). Higher incidence of composite resin cohesive failures was observed in the R-treated specimens (MT, LT), with and without aging. SEM images showed a rougher surface for B-treated specimens, while no changes were observed for the other treatments. XPS analysis showed a nanofilm of silica deposited over the zirconia surface after silica deposition. RT-ALD was an effective technique to deposit silica on the surface of zirconia, generating bond strength results similar to alumina-blasted specimens.

Room-temperature atomic layer deposition of iron oxide using plasma excited humidified argon

Room-temperature atomic layer deposition (RT-ALD) of iron oxide is developed with a precursor of bis(N, N′-diisopropyl-propionamidinate)iron [(DIPPA)2Fe] and plasma excited humidified Ar. Saturated conditions of (DIPPA)2Fe and plasma excited humidified Ar exposures at room temperature (23–25 °C) are investigated by in situ IR absorption spectroscopy for finding the RT-ALD process condition. Using the designated process, the growth per cycle of the iron oxide RT-ALD is confirmed as 0.15 nm/cycle based on the film thicknesses measured by the spectroscopic ellipsometer. The x-ray photoelectron spectroscopy suggests that the stoichiometry of the deposited iron oxide is closed to that of Fe2O3. The grown film is composed of partly crystallized iron oxides, confirmed by cross-sectional TEM and AFM. The RT deposited iron oxide exhibits a magnetic volume susceptibility of 1.52, which implies the applicability of the present coating for magnetic drug delivery. We discuss the surface reaction with the IR absorption spectroscopy and the quartz crystal microbalance. The (DIPPA)2Fe molecule is suggested to adsorb on the Fe2O3 surface with mixed first- and second-order reactions at RT. It is also suggested that amidinate ligands in (DIPPA)2Fe are released in the course of the adsorption and the remaining ligands are oxidized by the plasma excited humidified Ar. The RT iron oxide deposition is demonstrated, and the reaction mechanism of room-temperature ALD is discussed in this paper.

Silica deposition on zirconia via room-temperature atomic layer deposition (RT-ALD): Effect on bond strength to veneering ceramic

PurposeTo develop and to characterize a hybrid interface between yttria-stabilized zirconia (Y-TZP) transformed layer and silica-based nanofilm to enable a better bonding between Y-TZP and a veneering ceramic. Material and methodsSixty-six fully-sintered rectangular Y-TZP specimens were distributed into 6 groups, according to the surface treatment applied: C (control): no treatment; Al: 27 μm-alumina particle abrasion; Ht: hydrothermal treatment in autoclave for 15h; Si20: 20 cycles of silica deposition using room-temperature atomic layer deposition (RT-ALD); Si40: 40 cycles of RT-ALD; Ht + Si40: hydrothermal treatment followed by 40 cycles of RT-ALD. RT-ALD was performed by the sequential exposure of specimens to vapor of tetramethoxysilane orthosilicate (TMOS) and ammonium hydroxide (NH4OH). Y-TZP surface wettability and shear bond strength (SBS) between Y-TZP and the veneering ceramic were analyzed for all groups after surface treatments. One-way ANOVA and Tukey's HSD test were used for data analysis (p ≤ 0.05). ResultsThe highest contact angle was observed for the control group (64.46 ± 6.09 θ), while the lowest values (p < 0.001) were presented after Si20 (29.85 ± 4.23 θ) and Si40 (30.37 ± 5.51 θ) treatments. Hydrothermal treatment (49.3 ± 2.69 θ) and alumina abrasion (45.84 ± 4.12 θ) resulted in intermediate contact angle values. The highest SBS values were observed for Al (16.74 ± 1.68 MPa) and Ht (15.27 ± 2.11 MPa) groups (p < 0.018). Groups Si20 (9.66 ± 1.22 MPa), Si40 (9.33 ± 2.11 MPa), Ht + Si40 (9.37 ± 1.02 MPa) and C (12.54 ± 2.64 MPa) all resulted in similar SBS results (p > 0.998). ConclusionThe experimental treatments proposed enhanced surface wettability, but shear bond strength between Y-TZP and veneering ceramic was not improved. Alumina particle-abrasion improved SBS values while a decrease in wettability was observed.

Mechanical performance of a hybrid zirconia developed through hydrothermal treatment and Room-Temperature Atomic Layer Deposition (RT-ALD)

ObjectiveA silica-based nanofilm has been successfully deposited via Room-Temperature Atomic Layer Deposition (RT-ALD) on the surface of a glass. The purpose of this study was to evaluate the mechanical performance of a hybrid interface created between yttria-stabilized zirconia (Y-PSZ) transformed layer and silica-based nanofilm via RT-ALD. Material and methodsFully-sintered Y-PSZ (14 × 4.0 × 1.5 mm) specimens in different translucencies (MO, MT, LT; IPS e.max Zircad, Ivoclar Vivadent) were distributed in 5 groups: control (C - no treatment); hydrothermal treatment (HT- 15h, 134°C, 2 bar); alumina blasting (B - 50 μm Al2O3); RT-ALD silica deposition (S); HT followed by silica deposition (HTS). RT-ALD cycles consisted of the sequential exposure of specimens to tetramethoxysilane orthosilicate (TMOS - 60s) and ammonium hydroxide (NH4OH - 10 min) vapors in 40 cycles. Mechanical performance was analyzed by flexural strength (FS) (n = 10) and fatigue failure load (staircase method; n = 20) tests. Surface hardness (H) and Young's modulus (YM) were analyzed by nanoindentation. For surface chemical and topographical characterization, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were performed. Data from surface H, YM, FS, and fatigue limit (FL) were analyzed by two-way analysis of variance (ANOVA). ResultsThe interaction between material and treatment had a significant effect on FS (p < 0.001). The FS values ranged from 436.23 MPa to 856.65 MPa. HT resulted in the highest FS (856.65 MPa) for LT and the lowest FS (436.23 MPa) for MO zirconia. For all materials, S and B treatments resulted in similar FS values (p > 0.410). S did not affect FL when compared to the C group (p > 0.277) for any material investigated. HTS resulted in higher FL than S for LT and MO materials (p < 0.001). Surface hardness and modulus were similar between control and S-treated specimens for all materials analyzed. XPS analysis showed homogeneous silica content after 20 and 40 RT-ALD cycles, and SEM did not show significant changes in surface morphology between C and S-treated specimens. ConclusionRT-ALD resulted in effective silica deposition without any deleterious effect on zirconia-based materials mechanical properties. Alumina blasting promoted higher alteration on surface topography. HT prior to S resulted in superior FL (for MO and MT) and flexural strength (MO) for some of the materials investigated.

Flexible Al-Ti-Zn-O MIM capacitors fabricated by room temperature atomic layer deposition and their electrical performances

We pioneered to employ room temperature atomic layer deposition (RTALD) to fabricate flexible Al-Ti-O based metal-insulator-metal (MIM) capacitors on three polymer substrates of polyethylene terephthalate (PET), polyimide (PI) and epoxy resin (epoxy) without any post-processing. Zn was introduced to Al-Ti-O dielectrics to tune its electrical properties through varying ALD cycle ratio and cycle number. Under the optimal processing, the flexible MIM capacitors of Al1.56Ti0.47Zn0.06O3 exhibits comprehensively better performance such as higher capacitance density of 7.4 fF/μm2, smaller leakage current density of 2 × 10−8 A/cm2 at 3 V, and reasonable quadratic voltage linearity of 422 ppm/V2. X-ray photoelectron spectroscopy analyses reveal that the incorporation of a slight amount of Zn into Al-Ti-O dielectrics significantly decreases the oxygen vacancy concentration from 6.7% to 0.8%, beneficial for the improvement of electrical performance. Furthermore, our 2 × 2 cm2 flexible MIM capacitors could bear 4000 bending cycles at bending radius of 8.2 mm, showing better electrical stability. These results indicate that RTALD-derived Al-Ti-Zn-O dielectrics are competitive MIM capacitor candidates for flexible electronics and wearable devices. RTALD technology exhibits exciting potentials in flexible electronic device fabrication.

Study on fabrication method of composite oxide by room temperature atomic layer deposition

Thin films can be used to improve the surface properties of materials, enhancing elements such as absorption, abrasion resistance and corrosion resistance, for example. These thin films provide the foundation for a variety of applications in various fields and their applications depend on their morphology and stability, which is influenced by how they are deposited. Thin films can be deposited in different ways. One of these is a technology called atomic layer deposition (ALD). Professor Fumihiko Hirose, a scientist based at the Graduate School of Science and Engineering, Yamagata University, Japan, is conducting research on the room temperature ALD of oxide metals. Along with his team, Professor Hirose has developed a new and improved way of performing ALD to create thin films, and the potential applications are endless.

Gas Diffusion Barrier of Vapor Phase Infiltrated Pen with Room Temperature ALD

Metal oxides like aluminum oxide (Al2O3) and silicon oxide (SiO2) are well known as gas barrier materials to moisture. The gas barrier films are used in various applications like food packaging, pharmaceuticals, chemicals, and organic electronics. Especially in the field of organic electronics, the high gas barrier performance is essential to avoid organic semiconducting material degradation from moisture. Because of the most attractive point in these devices is their possibility that of flexible device fabrication, we must use a flexible polymer film substrate. The polymer film substrate is thermally fragile, and it includes voids in polymer chains. From this, we have to deposit the gas barrier film at low temperature and uniformly coat the voids. To overcome these problems, we developed the room-temperature atomic layer deposition (RT-ALD) technologies. In this study, we examine gas barrier coatings with a combination of vapor phase infiltration (VPI) for higher barrier performances. The VPI produces a polymer-inorganic hybrid layer by infiltrating inorganic materials into polymer substrates in the subsurface region. It is possible to fill in the voids in polymer substrates.For VPI, we used tris(dimethylamino)silane (TDMAS) as the infiltration gas and plasma excited humidified Ar as oxidation gas. The infiltration process was operated at room temperature of 25 °C. The PEN film was infiltrated by being kept in a vacuum chamber with a TDMAS pressure of 200 Pa for 6 hours. After infiltration, the PEN films were exposed to plasma excited humidified Ar to oxidize surface absorbant. In the RT ALD, we used trimethylaluminum (TMA) and dimethylzinc (DMZ) as the precursor and oxidation gas was the same as VPI. We fabricated the gas barrier films with a ZnO single layer and a laminated Al2O3/ ZnO.In figure 1, we show Si 2p narrow scan spectra of TDMAS infiltrated PEN by X-ray photoelectron spectroscopy. The Si 2p peak existed after 90 min Ar bombardment etching. It indicates the TDMAS molecules penetrated in the PEN film. We also confirmed that its surface became smooth and its morphology was changed by using AFM. The surface modification by VPI was evaluated with a water contact angle meter. In this paper, we will release the WVTR data and discuss its performance compared with the pristine PEN. Figure 1

Room-Temperature Atomic Layer Deposition of Aluminum Silicate and its Application to Na- and K-Ion Sorption

Room-temperature (RT) atomic layer deposition (ALD) of aluminum silicate is developed with a successive adsorption process of tris(dimethylamino)silane (TDMAS) and trimethylaluminum (TMA) using an oxidizer of plasma-excited humidified Ar. The Si-to-Al atomic ratio in the deposited film is controlled by the ratio of TMA and TDMAS exposures. RT deposition of the aluminum silicate film on Si and polyethylene naphthalate films is demonstrated. The ion sorption ability of Na and its exchange with K are demonstrated on the RT-deposited aluminum silicate. The ion sorption of Na in a NaCl solution is maximum when the Si atomic content is balanced with that of Al. The applicability of the RT-deposited aluminum silicate as an ion-sensing surface is discussed.

Room temperature atomic layer deposition of nano crystalline ZnO and its application for flexible electronics

Room temperature atomic layer deposition of nano crystalline ZnO and its application for flexible electronics

Room temperature atomic layer deposition of niobium oxide using plasma excited humidified argon and its application to anticorrosion to hydrochloric acid

Room temperature (RT) atomic layer deposition (ALD) of Nb2O5 is developed using (tert-butylimido)tris(ethylmethylamido)niobium and a plasma excited humidified Ar. To design the process condition, an in situ monitoring system of IR absorption spectroscopy (IRAS) is utilized to observe the surface saturation of precursors. Based on the saturation characteristics of precursors measured from IRAS, the gas injection condition and oxidization time are determined, where the RT Nb2O5 deposition with a growth per cycle of 0.11 nm is confirmed by x-ray photoelectron spectroscopy and spectroscopic ellipsometry. The RT deposited Nb2O5 film exhibits clear anticorrosion to hydrochloric acid. The reaction mechanism of ALD growth and the applicability of anticorrosion film with RT deposited N2O5 are discussed in this paper.

Electrical Properties of Low-Temperature Processed Sn-Doped In2O3 Thin Films: The Role of Microstructure and Oxygen Content and the Potential of Defect Modulation Doping

Low-temperature-processed ITO thin films offer the potential of overcoming the doping limit by suppressing the equilibrium of compensating oxygen interstitial defects. To elucidate this potential, electrical properties of Sn-doped InO (ITO) thin films are studied in dependence on film thickness. In-operando conductivity and Hall effect measurements during annealing of room-temperature-deposited films, together with different film thickness in different environments, allow to discriminate between the effects of crystallization, grain growth, donor activation and oxygen diffusion on carrier concentrations and mobilities. At , a control of carrier concentration by oxygen incorporation or extraction is only dominant for very thin films. The electrical properties of thicker films deposited at room temperature are mostly affected by the grain size. The remaining diffusivity of compensating oxygen defects at is sufficient to screen the high Fermi level induced by deposition of AlO using atomic layer deposition (ALD), which disables the use of defect modulation doping at this temperature. The results indicate that achieving higher carrier concentrations in ITO thin films requires a control of the oxygen pressure during deposition in combination with seed layers to enhance crystallinity or the use of near room temperature ALD.

Surface reaction kinetics of room temperature atomic layer deposition of ZnO observed by in situ IR absorption spectroscopy

Room temperature (RT) atomic layer deposition (ALD) of ZnO is developed by using a precursor of dimethyl zinc (DMZ) and plasma excited humidified argon. Surface reactions of RT ALD of ZnO are investigated by an in situ observation of multiple internal reflection IR absorption spectroscopy. The saturation condition of DMZ and plasma excited humidified argon is discussed by the IR absorbance spectra measured from the sample surface. In the ALD experiment, the grown film is identified as the fully oxidized ZnO by x-ray photoelectron spectroscopy. The growth per cycle is measured to be 0.046 nm/cycle. In this paper, the authors will discuss the mechanism of surface reaction in the ALD process.

Near room temperature atomic layer deposition of ZnO thin films on poly (methyl methacrylate) (PMMA) templates: A study of structure, morphology and photoluminescence of ZnO as an effect of template confinement

ZnO thin films were grown on confined Poly (methyl methacrylate) (PMMA) templates, with high coverage and sharp interface, by atomic layer deposition (ALD) at near room temperature (at 35 °C). Crystalline ZnO films, with c-axis orientation along surface normal, were formed on PMMA templates. With decreasing PMMA template thickness, from 80 nm (5Rg, Rg ∼ 16 nm, the radius of gyration of PMMA) to 32 nm (2Rg) and below (5 nm, 0.3Rg), the photoluminescence (PL) of ALD grown ZnO films changes significantly. Pronounced deep level emission (DLE), corresponding to the oxygen vacancy related defect level (VO++) of ZnO grown on 5Rg PMMA, reduced noticeably for ZnO on 2Rg PMMA and below. Furthermore, in the near-band-edge emission (NBE) of ZnO, the contribution of free-exciton (FX) with respect to its phonon replica (FX-2LO) increased with reduction of PMMA template thickness from 5Rg to 2Rg or below. The observed trend of the photoluminescence spectra indicates significant reduction of surface induced defects in the ZnO nanostructures, formed on the thinner PMMA templates (2Rg and 0.3Rg) and can be ascribed to the formation of smaller ZnO nanoparticles on 5Rg PMMA, which is consistent with the results obtained from structure and surface morphology study.

In situ XPS study of low temperature atomic layer deposition of B2O3 films on Si using BCl3 and H2O precursors

In this study, atomic layer deposition (ALD) of nanoscale boron oxide (B2O3) films on Si using BCl3/H2O precursors at room temperature was investigated using in situ x-ray photoelectron spectroscopy (XPS). B2O3 thin films are of considerable interest in ultra-shallow Si doping applications, including high aspect ratio FinFET structures, where film conformality and precise thickness control are crucial. ALD is therefore of particular interest for such applications. XPS data demonstrate that initial BCl3 exposures on Si at room temperature are self-limiting and are accompanied by partial B-Cl dissociation and Cl-Si formation. H2O exposures &amp;gt;1.7 × 108 Langmuir at room temperature removed Cl from B sites, but failed to remove Cl from the Cl-Si species. ALD-type growth of B2O3 was observed with an average growth rate of ∼2.5 Å/cycle and without further increase in the Cl content. The initial Cl contamination was due to Cl-Si bond formation at the interface, without Cl incorporation into the oxide film. The role of Cl in the inhibition of oxide film growth was further investigated by the reactions of BCl3/O2 on SiO2 at room temperature and 650 K. BCl3/O2 precursors exhibit negligible B2O3 growth at room temperature. At 650 K, B2O3 growth was observed with a decreasing growth rate per BCl3/O2 cycle, corresponding to an increase in the Cl:B atomic ratio. These data indicate that room temperature ALD using BCl3/H2O precursors is a potential route toward the formation of uniform B2O3 films for shallow Si doping applications, but that Cl-Si formation significantly impacts initial oxide nucleation and growth.

Enhanced Bioactivity of Collagen Fiber Functionalized with Room Temperature Atomic Layer Deposited Titania.

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 TiO2 thin film on the collagen fibrillar surface, and consequently, the fibers became thicker making the membrane pores smaller. The in vitro bioactivity of the ALD-TiO2 thin 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.