Precursor Exposure Time Research Articles

Comparative Study of Plasma-Enhanced-Atomic-Layer-Deposited Al2O3/HfO2/SiO2 and HfO2/Al2O3/SiO2 Trilayers for Ultraviolet Laser Applications.

High-performance thin films combining large optical bandgap Al2O3 and high refractive index HfO2 are excellent components for constructing the next generation of laser systems with enhanced output power. However, the growth of low-defect plasma-enhanced-atomic-layer-deposited (PEALD) Al2O3 for high-power laser applications and its combination with HfO2 and SiO2 materials commonly used in high-power laser thin films still face challenges, such as how to minimize defects, especially interface defects. In this work, substrate-layer interface defects in Al2O3 single-layer thin films, layer-layer interface defects in Al2O3-based bilayer and trilayer thin films, and their effects on the laser-induced damage threshold (LIDT) were investigated via capacitance-voltage (C-V) measurements. The experimental results show that by optimizing the deposition parameters, specifically the deposition temperature, precursor exposure time, and plasma oxygen exposure time, Al2O3 thin films with low defect density and high LIDT can be obtained. Two trilayer anti-reflection (AR) thin film structures, Al2O3/HfO2/SiO2 and HfO2/Al2O3/SiO2, were then prepared and compared. The trilayer AR thin film with Al2O3/HfO2/SiO2 structure exhibits a lower interface defect density, better interface bonding performance, and an increase in LIDT by approximately 2.8 times. We believe these results provide guidance for the control of interface defects and the design of thin film structures and will benefit many thin film optics for laser applications.

Exploring the Vapor Phase Infiltration of Trimethylaluminum into Polyacrylonitrile Fabrics

Vapor phase infiltration (VPI) creates a hybrid organic-inorganic material by modifying the bulk of a polymer substrate with a metalorganic vapor phase precursor. In VPI, the metalorganic precursor sorbs to the polymer, then diffuses through the bulk and becomes entrapped—either by a chemical bond between the polymer and the inorganic or by a co-reaction with a second species—yielding a hybrid composed of the polymer and, often, a metal oxide. Some of the polymers that have been studied under VPI include poly(methyl methacrylate) (PMMA), polyethylene terephthalate (PET), polydimethyl siloxane (PDMS), and poly(3-hexylthiophene) (P3HT). There is a notable exception in this list: polyacrylonitrile (PAN). The high reactivity of the nitrile functional group on the backbone of the PAN polymer chain suggests PAN would perform well in VPI. PAN is used in textiles and filtration, but one of its most common applications is as a precursor to carbon fiber. Previous hybrid materials created via VPI have demonstrated new optical and thermal properties that differ from the neat polymer. If infiltrated successfully, these properties in PAN could be of use in its application spaces. In this work, we expand the VPI material space with the first study of infiltration of PAN. To explore the bounds of this system in terms of achievable inorganic loadings and hybrid material chemical structure, PAN is infiltrated with the metalorganic precursor trimethylaluminum (TMA) and co-reacted with water vapor under variable precursor exposure times, precursor desorption times, and processing temperatures. PAN is found to infiltrate with high quantities of inorganic loading (as measured by thermogravimetric analysis) that can be tuned from 1% to 17% inorganic by weight. Inorganic loading depends strongly on precursor exposure time with a sample processed at 140℃ showing a 25% increase when the exposure time is increased from 5 hours to 25 hours. Infiltration temperature also plays a significant role with hybrid materials demonstrating a 78% increase in inorganic loading when the PAN processing temperature is increased from 80℃ to 140℃. The apparent increase in inorganic loading with temperature may be related to the mass transport and reaction kinetics of the system under VPI conditions. Precursor desorption time, on the other hand, has minimal impact on inorganic loading suggesting most sorbed precursor participates in a chemical interaction with the polymer during infiltration. In exploring the resulting AlOx/PAN hybrid chemical structure with FTIR, this mechanism was supported by an observed decrease of the PAN nitrile peak at ~2240 cm-1 that scaled with inorganic loading. These structural changes in inorganic loading and chemical state are found to directly correspond to the optical (UV-Vis) and thermal (TGA) properties of the hybrid materials. The results of these characterization techniques imply that the VPI process causes a significant chemical change to the PAN fabric and suggests the process could possibly induce PAN cyclization, which may be advantageous for carbon fiber applications. Overall, this work establishes the significant and tunable inorganic loading of AlOx/PAN hybrid fabrics and expands VPI to a new polymer system.

Spatial ALD of Al2O3 and ZnO using heavy water

Al2O3 and ZnO thin films were deposited from trimethylaluminium (TMA) and diethylzinc (DEZ) in combination with water using cylindrical rotating substrate spatial atomic layer deposition (SALD). The depositions were done between 67 and 140 °C. The growth per cycle for Al2O3 varied between 0.75 and 2.0 × 1015 at./cm2 per cycle and for ZnO between 0.52 and 1.07 × 1015 at./cm2 per cycle. The hydrogen incorporation was studied by varying the deposition temperature and substrate rotation speed. The rotation speed affects the precursor exposure time (46–458 ms) and inert gas purging time (111–1120 ms). The results show that Al2O3 films can contain up to 25 at.% of hydrogen when the deposition temperature is 67 °C or the deposition exposure/purging times are short. The deposition of ZnO in similar conditions produces films with hydrogen concentrations up to 15 at.%. The source of impurity hydrogen was investigated by using heavy water, 2H2O, as an oxygen source. The main hydrogen isotope in the Al2O3 films at low temperatures and fast deposition speed was found to be 1H, while at higher temperatures and lower deposition speeds 2H isotope was dominant. For ZnO, 1H was the majority hydrogen isotope in the films in all the studied deposition conditions except at the lowest rotation speed.

Impact of trimethylaluminum exposure time on the mechanical properties of single-cycle atomic layer deposition modified cellulosic nanopaper

Cellulosic nanomaterials can improve the performance of various products and can be renewably sourced. In this study, nanocellulosic paper (nanopapers) is chemically and physically altered with simple gas-phase processing to achieve enhanced mechanical performance. Cellulosic nanofibril paper is exposed to single cycles of trimethylaluminum (TMA) and water to modify the surface and subsurface chemistry with small quantities of aluminum oxide. Precursor exposure times are found to significantly influence the amount of inorganic deposited within the cellulosic structure and its crystallinity. This result differs from the common assumption that exposing cellulose to TMA will lead to an “atomic layer deposition (ALD)” type of process in which self-limited surface saturation is quickly achieved. These results suggest that with extended exposure times, the TMA precursor finds new pathways to chemically or physically alter the cellulosic material. Through the x-ray photoelectron spectroscopy analysis, we find that cellulose undergoes a decomposition process during the TMA exposure and/or subsequent reaction with H2O, creating at least one additional pathway to inorganic uptake. Interestingly, uniaxial tensile strength measurements reveal that longer TMA exposure times significantly increase the nanopaper's elongation at break and ultimate tensile strength, with only a modest loss in Young's modulus. While similar inorganic loading can be achieved with multiple ALD cycles, mechanical toughness exhibits significantly less change than for the increased TMA exposure times. X-ray diffraction suggests that the TMA exposures are transforming crystalline portions of the nanocellulose into amorphous structures. These amorphous regions lead to crazing, which increases the strain to break and toughness of the nanopaper.

HfO2/SiO2 anti-reflection films for UV lasers via plasma-enhanced atomic layer deposition

The laser-induced damage threshold (LIDT) of HfO2/SiO2 anti-reflection (AR) films for ultraviolet (UV) lasers was improved via low-temperature plasma-enhanced atomic layer deposition (PEALD). Focused on the chemical composition, optical absorption, surface scattering, and laser-resistance, the impact of precursor exposure time on PEALD SiO2 film properties and growth temperature on PEALD SiO2 and HfO2 film properties were investigated respectively. When irradiated by UV laser, PEALD SiO2 film exhibits a higher LIDT than the PEALD HfO2 film, which is consistent with their less impurity content and lower absorption. A bilayer structure HfO2/SiO2 AR film for 355 nm laser was designed and experimentally demonstrated via PEALD growth at a temperature of 150 °C. The prepared PEALD AR film shows a reflectance <0.2% at 355 nm as designed and better laser-damage resistance with a LIDT of 24.4 J/cm2 (355 nm, 7.8 ns) than the conventional e-beam deposition method.

Deposition and properties of mixed molybdenum sulfide (MoS2) and copper sulfide (CuxS) films on glass surface using elemental sulfur as a precursor

Mixed molybdenum sulfide (MoS2) and copper sulfide (CuxS) materials were synthesized on glass slides as a model substrate by successive ionic layer adsorption and reaction method using elemental sulfur as a sulfur source and solutions of copper (II/I) and molybdenum (IV) salts. X-ray diffraction data showed the presence of copper sulfides (anilite Cu7S4 and djurleite Cu31S16 phases), molybdenum disulfide and molybdenum oxide with adjustable crystalline phase composition dependent on the precursor exposure time and reaction temperature. Scanning electron microscopy images showed that the surface had a homogenous layer distribution at lower temperatures/short exposures and comprised of ~1 μm particles. X-ray photoelectron spectroscopy showed no oxidized sulfate (SO42−) compounds present on the sample surface while a thin MoO3 layer was found to cover the sample surface. Optical ultraviolet-visible spectroscopy showed mixed layers formed, containing optical properties of both MoS2 and CuxS. After annealing in an N2 atmosphere at 100 °C, the sample was composed primarily of MoS2 and copper sulfides in the crystalline phase with minimal residual S8. Usability of this mild mixed metal sulfide thin film preparation method on supports for sour natural gas catalyst synthesis is also discussed.

Fast Charging of Chlorine Doped Amorphous TiO2 Reaching 1 Li per TiO2 for Sub-Micron Thick Films

Negative electrodes from TiO2 remains an intriguing choice for lithium-ion batteries, as it could offer a high theoretical capacity (336 mAh/g) and excellent cycling stability. Unfortunately, due to its low electronic and ionic conductivity, state-of-the-art nanosized (< 20 nm) TiO2 electrodes still only achieve about 75% of this capacity at 1 C (or 336 mA/g). From submicron sizes on, TiO2 almost no accessible capacity is left at practical C-rates. In this work, submicron thick chlorine doped amorphous TiO2 (TiO2-xClx) films are investigated as a high-performance Li+-ion insertion electrode material. The TiO2-xClx films were fabricated by Spatial Atomic Layer Deposition (S-ALD), by which the chlorine content was controlled by varying the deposition temperature and gas precursor exposure time, as determined by Rutherford Backscatter Spectroscopy (RBS) and X-Ray Photoelectron Spectroscopy (XPS). Electrochemical tests revealed a maximum reversible Li+-ion insertion/extraction capacity of 362 mAh/g at 0.25 C for the TiO1.912Cl0.088 film (see Fig. 1), which is above the theoretical maximum and suggests that reduction of Ti(III) to Ti(II) is accessible in Cl-doped amorphous TiO2. At a rate of 1 C, still 90% (301 mAh/g) of the theoretical TiO2 capacity is achieved and even 27% (92 mAh/g) at 50 C (see Fig. 1). In addition, TiO2-xClx films deposited by S-ALD are demonstrated as three-dimensional (3D) thin-film electrodes for 3D solid-state batteries. Using 3D structuring, the footprint capacity increased 24 times, while the excellent rate-performance of the planar TiO2-xClx films is retained. The cycling stability of the 3D TiO1.912Cl0.088 electrode was tested for 1000 cycles at 10 C, and no degradation in capacity is observed. Finally, benchmarking our 3D thin-film TiO1.912Cl0.088 electrode shows that it outperforms all other 3D thin-film TiO2 electrodes previously reported. Figure 1

Atomic Layer Deposition for Coating of High Aspect Ratio TiO2 Nanotube Layers.

We present an optimized approach for the deposition of Al2O3 (as a model secondary material) coating into high aspect ratio (≈180) anodic TiO2 nanotube layers using the atomic layer deposition (ALD) process. In order to study the influence of the diffusion of the Al2O3 precursors on the resulting coating thickness, ALD processes with different exposure times (i.e., 0.5, 2, 5, and 10 s) of the trimethylaluminum (TMA) precursor were performed. Uniform coating of the nanotube interiors was achieved with longer exposure times (5 and 10 s), as verified by detailed scanning electron microscopy analysis. Quartz crystal microbalance measurements were used to monitor the deposition process and its particular features due to the tube diameter gradient. Finally, theoretical calculations were performed to calculate the minimum precursor exposure time to attain uniform coating. Theoretical values on the diffusion regime matched with the experimental results and helped to obtain valuable information for further optimization of ALD coating processes. The presented approach provides a straightforward solution toward the development of many novel devices, based on a high surface area interface between TiO2 nanotubes and a secondary material (such as Al2O3).

Enhancing the platinum atomic layer deposition infiltration depth inside anodic alumina nanoporous membrane

Nanoporous platinum membranes can be straightforwardly fabricated by forming a Pt coating inside the nanopores of anodic alumina membranes (AAO) using atomic layer deposition (ALD). However, the high-aspect-ratio of AAO makes Pt ALD very challenging. By tuning the process deposition temperature and precursor exposure time, enhanced infiltration depth along with conformal coating was achieved for Pt ALD inside the AAO templates. Cross-sectional scanning electron microscopy/energy dispersive x-ray spectroscopy and small angle neutron scattering were employed to analyze the Pt coverage and thickness inside the AAO nanopores. Additionally, one application of platinum-coated membrane was demonstrated by creating a high-density protein-functionalized interface.

Modeling precursor diffusion and reaction of atomic layer deposition in porous structures

Atomic layer deposition (ALD) is a technique for depositing thin films of materials with a precise thickness control and uniformity using the self-limitation of the underlying reactions. Usually, it is difficult to predict the result of the ALD process for given external parameters, e.g., the precursor exposure time or the size of the precursor molecules. Therefore, a deeper insight into ALD by modeling the process is needed to improve process control and to achieve more economical coatings. In this paper, a detailed, microscopic approach based on the model developed by Yanguas-Gil and Elam is presented and additionally compared with the experiment. Precursor diffusion and second-order reaction kinetics are combined to identify the influence of the porous substrate's microstructural parameters and the influence of precursor properties on the coating. The thickness of the deposited film is calculated for different depths inside the porous structure in relation to the precursor exposure time, the precursor vapor pressure, and other parameters. Good agreement with experimental results was obtained for ALD zirconiumdioxide (ZrO2) films using the precursors tetrakis(ethylmethylamido)zirconium and O2. The derivation can be adjusted to describe other features of ALD processes, e.g., precursor and reactive site losses, different growth modes, pore size reduction, and surface diffusion.

Plasma‐Assisted Atomic Layer Deposition of PtOx from (MeCp)PtMe3 and O2 Plasma

AbstractAtomic layer deposition (ALD) using (MeCp)PtMe3 and O2 gas or O2 plasma is a well‐established technique for the deposition of thin films of Pt, but the potential of ALD to deposit platinum oxide (PtOx) has not yet been systematically explored. This work demonstrates how PtOx can be deposited by plasma‐assisted (PA)‐ALD in a temperature window from room temperature (RT) to 300 °C by controlling the O2 plasma and (MeCp)PtMe3 exposure. With increasing substrate temperature, the thermal stability of PtOx decreases and the reducing activity of the precursor ligands increases. Therefore, longer O2 plasma exposures and/or lower (MeCp)PtMe3 exposures are required to obtain PtOx at higher temperatures. Furthermore, it is established that, during the nucleation stage, PtOx ALD starts by the formation of islands that grow and coalesce during the initial ∼40 cycles. Closed‐layer thin films of PtOx with an O/Pt ratio of 2.5 can be deposited at 100 °C with a minimal thickness of only ∼2 nm. It is also demonstrated that a conformality of ∼90% can be reached for PtOx films in trenches with an aspect ratio of 9 when using optimized O2 plasma and precursor exposure times.

Design Considerations for ZnO Transistors Made Using Spatial ALD

We have used spatial atomic layer deposition (SALD) to fabricate a variety of thin film transistors using zinc oxide as the semiconductor and aluminum oxide as the insulator. The conductive electrodes are formed either from aluminum-doped zinc oxide, or from thermally evaporated metals. Spatial ALD can be performed at atmospheric pressure, and can grow coatings very quickly. Deposition occurs without a requirement for valve timing, by moving the substrate relative to the precursors flowing from a coating head. The proximity of the substrate to the coating head is controlled via a gas bearing design – allowing SALD to operate with purge times that are equivalent to the precursor exposure times (sub-second) unlike traditional chamber-based systems. In this talk we will discuss examples of thin film electronics with architectures that are enabled by ALD, with a particular focus on spatial ALD. We use the well known conformality of ALD to build self-aligned, sub-micron channel length, vertical transistors. The vertical transistor electrical performance is impressive compared to amorphous silicon TFTs, for example, yet the alignment tolerances inherent in the fabrication process are large.Our second approach to fabricating devices uses selective area deposition, with inkjet-printed inhibitor, to pattern all the active layers. We build full transistors and circuits using one inhibitor ink, the SALD system, and an oxygen plasma to clean the substrate. Performance of the resulting transistors and circuits match photolithographically patterned ones.

Effect of Reaction Mechanism on Precursor Exposure Time in Atomic Layer Deposition of Silicon Oxide and Silicon Nitride

Atomic layer deposition (ALD) of highly conformal, silicon-based dielectric thin films has become necessary because of the continuing decrease in feature size in microelectronic devices. The ALD of oxides and nitrides is usually thought to be mechanistically similar, but plasma-enhanced ALD of silicon nitride is found to be problematic, while that of silicon oxide is straightforward. To find why, the ALD of silicon nitride and silicon oxide dielectric films was studied by applying ab initio methods to theoretical models for proposed surface reaction mechanisms. The thermodynamic energies for the elimination of functional groups from different silicon precursors reacting with simple model molecules were calculated using density functional theory (DFT), explaining the lower reactivity of precursors toward the deposition of silicon nitride relative to silicon oxide seen in experiments, but not explaining the trends between precursors. Using more realistic cluster models of amine and hydroxyl covered surfaces, the structures and energies were calculated of reaction pathways for chemisorption of different silicon precursors via functional group elimination, with more success. DFT calculations identified the initial physisorption step as crucial toward deposition and this step was thus used to predict the ALD reactivity of a range of amino-silane precursors, yielding good agreement with experiment. The retention of hydrogen within silicon nitride films but not in silicon oxide observed in FTIR spectra was accounted for by the theoretical calculations and helped verify the application of the model.

Selective Area Spatial Atomic Layer Deposition of ZnO, Al2O3, and Aluminum-Doped ZnO Using Poly(vinyl pyrrolidone)

Spatial atomic layer deposition (SALD) is gaining traction in the thin film electronics field because of its ability to produce quality films at a fraction of the time typically associated with ALD processes. Here, we explore the process space for the fabrication of thin film patterned-by-printing electronics using the combination of SALD and selective area patterning. First, a study of SALD growth conditions for the three primary components of our metal oxide thin film electronics, namely alumina (Al2O3) dielectric, zinc oxide (ZnO) semiconductor, and aluminum doped ZnO (AZO) conductor, provides insight into the potential trade-offs in performance, substrate latitude (temperature), and process speed. At constant precursor partial pressures, the precursor exposure times and substrate temperatures were varied from 25 to 400 ms and from 100 to 300 °C, respectively. The very short gas exposure and purge times obtainable only with a spatial implementation of ALD are shown always to be advantageous for through...

Conformality of thermal and plasma enhanced atomic layer deposition on a non-woven fibrous substrate

Alumina was deposited on a non-woven polyester fiber substrate using both thermal and plasma enhanced atomic layer deposition (ALD). The textile was confined inside a one dimensional test structure. The coverage of the ALD film on the nonwoven as a function of depth in the test structure was determined by energy dispersive X-ray spectroscopy (EDX). A model is introduced which links the precursor transport in the nonwoven (transmission, reflection and deposition) with the nonwoven properties (density, fiber surface area, density of surface sites). The experimental results are compared to simulations of the coverage profile. It is shown that longer precursor exposure times result in deposition deeper inside the nonwoven. However, the majority of precursor molecules entering the nonwoven leave the test structure without contributing to film growth. ALD from TMA and oxygen plasma had a very limited penetration into the nonwoven because of radical recombination. This effect is relevant for plasma treatment of fibrous materials in general.

Use of a high-flow diaphragm valve in the exhaust line of atomic layer deposition reactors

In many atomic layer deposition (ALD) reactors, a stop valve is placed between the reaction chamber and the vacuum pump to allow for long precursor exposure times. This valve can lead to a reduction in conductance to the pump, lowering pumping efficiency and increasing the required purging time. In this study, a prototype high-flow (flow coefficient Cv = 1.7) diaphragm valve designed for ALD compatibility was inserted into the exhaust line of an ALD reactor and compared to a standard ALD diaphragm valve (Cv = 0.62). The results show that the chamber base pressure was reduced by 66% with the high-flow valve, which has implications for precursor delivery and mass transport. Furthermore, ZnO films were deposited via ALD, and the variation in thickness across a 100 mm diameter Si wafer was shown to be lower for the high-flow valve, especially with short purging times. These results suggest that the use of a high-flow ALD valve in the exhaust line can be beneficial when attempting to reduce the purging time and improve uniformity in research-scale reactors, and it could eventually be utilized in larger production-scale reactors.

Tuning the Composition and Nanostructure of Pt/Ir Films via Anodized Aluminum Oxide Templated Atomic Layer Deposition

AbstractNanostructured metal films have been widely studied for their roles in sensing, catalysis, and energy storage. In this work, the synthesis of compositionally controlled and nanostructured Pt/Ir films by atomic layer deposition (ALD) into porous anodized aluminum oxide templates is demonstrated. Templated ALD provides advantages over alternative synthesis techniques, including improved film uniformity and conformality as well as atomic‐scale control over morphology and composition. Nanostructured Pt ALD films are demonstrated with morphological control provided by the Pt precursor exposure time and the number of ALD cycles. With these approaches, Pt films with enhanced surface areas, as characterized by roughness factors as large as 310, are reproducibly synthesized. Additionally, nanostructured PtIr alloy films of controlled composition and morphology are demonstrated by templated ALD, with compositions varying systematically from pure Pt to pure Ir. Lastly, the application of nanostructured Pt films to electrochemical sensing applications is demonstrated by the non‐enzymatic sensing of glucose.

Tuning the Composition and Nanostructure of Pt/Ir Films via Anodized Aluminum Oxide Templated Atomic Layer Deposition

AbstractNanostructured metal films have been widely studied for their roles in sensing, catalysis, and energy storage. In this work, the synthesis of compositionally controlled and nanostructured Pt/Ir films by atomic layer deposition (ALD) into porous anodized aluminum oxide templates is demonstrated. Templated ALD provides advantages over alternative synthesis techniques, including improved film uniformity and conformality as well as atomic‐scale control over morphology and composition. Nanostructured Pt ALD films are demonstrated with morphological control provided by the Pt precursor exposure time and the number of ALD cycles. With these approaches, Pt films with enhanced surface areas, as characterized by roughness factors as large as 310, are reproducibly synthesized. Additionally, nanostructured PtIr alloy films of controlled composition and morphology are demonstrated by templated ALD, with compositions varying systematically from pure Pt to pure Ir. Lastly, the application of nanostructured Pt films to electrochemical sensing applications is demonstrated by the non‐enzymatic sensing of glucose.

Genesis and Evolution of Surface Species during Pt Atomic Layer Deposition on Oxide Supports Characterized by in Situ XAFS Analysis and Water−Gas Shift Reaction

Platinum atomic layer deposition (ALD) using MeCpPtMe3 was employed to prepare high loadings of uniform-sized, 1−2 nm Pt nanoparticles on high surface area Al2O3, TiO2, and SrTiO3 supports. X-ray absorption fine structure was utilized to monitor the changes in the Pt species during each step of the synthesis. The temperature, precursor exposure time, treatment gas, and number of ALD cycles were found to affect the Pt particle size and density. Lower-temperature MeCpPtMe3 adsorption yielded smaller particles due to reduced thermal decomposition. A 300 °C air treatment of the adsorbed MeCpPtMe3 leads to PtO. In subsequent ALD cycles, the MeCpPtMe3 reduces the PtO to metallic Pt in the ratio of one precursor molecule per PtO. A 200 °C H2 treatment of the adsorbed MeCpPtMe3 leads to the formation of 1−2 nm, metallic Pt nanoparticles. During subsequent ALD cycles, MeCpPtMe3 adsorbs on the support, which, upon reduction, yields additional Pt nanoparticles with a minimal increase in size of the previously formed...

Spatially controlled atomic layer deposition in porous materials

We describe a technique for depositing materials at controlled depths within porous substrates based upon the passivating effect produced by one precursor to prevent the adsorption of a second precursor. For example, a surface exposed to trimethyl aluminum is not reactive toward diethyl zinc. This effect, combined with Knudsen diffusion in which the precursor exposure times dictate the depth of penetration of the deposited layer, enables spatially controlled “stripe coating” within porous supports. We demonstrate ZnO stripes in anodic alumina and model the results using Monte Carlo simulations. Etching is identified as a potential problem for certain precursor combinations.