Top PDF ZnO THIN FILMS PREPARED BY ATOMIC LAYER DEPOSITION

ZnO THIN FILMS PREPARED BY ATOMIC LAYER DEPOSITION

ZnO THIN FILMS PREPARED BY ATOMIC LAYER DEPOSITION

ISSN 1335-0803 (print version) ISSN 1338-6174 (online version) 1. Introduction Zinc oxide belongs to the semiconductor group II-IV type. It is characterized by a wide energy gap of 3.37 eV (at room temperature). Such a wide energy gap makes ZnO completely transparent to the electromagnetic spectrum of visible light. It allows using of ZnO as the transparent conductive layers (TCL). The most commonly used material for such a coating is indium-tin-oxide (ITO). However, due to the high costs of production of ITO, which are mainly generated by the high price of indium, they are sought alternative materials [1 - 5].
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Fabrication of multilayer ZnO/Ti02/Zn0 thin films with enhancement of optical properties by atomic layer deposition (ALD)

Fabrication of multilayer ZnO/Ti02/Zn0 thin films with enhancement of optical properties by atomic layer deposition (ALD)

Hou, and K-L Choy, Enhancement of Crystallinity and Optical Properties of Bilayer Ti02 /ZnO Thin Films Prepared by Atomic Layer Deposition.. Patrick, Improvement in corrosion resistance [r]

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ABSTRACT: In this work, optical properties for thin doped ZnO films , prepared by pulse laser deposition (PLD)

ABSTRACT: In this work, optical properties for thin doped ZnO films , prepared by pulse laser deposition (PLD)

The ZnO is a wide and direct band gap semiconductor material [1].It has 3.37 eV energy gap at room temperature. Since ZnO gap energy lies in the ultraviolet (UV) range, ZnO is suitable for UV detection by using its photoconductivity properties [2]. The UV photodetector has a wide range of applications and it attracted great interest during the recent years. Most of the applications are directed toward the environmental monitoring, solar astronomy, and missile warning systems [3,4].Many different techniques such as organic chemical vapor deposition (MOCVD),chemical vapor deposition, plasma-assisted molecular beam epitaxy (PA-MBE), pulse laser deposition (PLD), and spray pyrolysis technique have been used to growth the ZnO[5-8].
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A Non-Destructive Method for Measuring the Mechanical Properties of Ultrathin Films Prepared by Atomic Layer Deposition

A Non-Destructive Method for Measuring the Mechanical Properties of Ultrathin Films Prepared by Atomic Layer Deposition

The elastic modulus values obtained in this work are comparable with literature values. Higher ALD deposition temperatures will produce stiffer films (cf. Table II ). As mentioned, nanoindentation usually requires films thicker than 100 nm as the indent depth should within 1/10 of the film thickness to neglect the influence of the substrate. If nanoindentation is used to obtain elastic modulus for films thinner than 100 nanometers, both continuous stiffness mea- surement and modeling are necessary. The nanobeam deflec- tion method requires a complicated sample fabrication. The films we measured using the LAW method, thickness rang- ing from 7.8 nm (50 reaction cycles) to 38 nm (250 reaction cycles), are much thinner than prior work. The measurement is simple and fast, as well as non-destructive. This method can be applied to most ALD films to obtain the elastic properties.
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Structural, electrical, and optical properties of Ti doped ZnO films fabricated by atomic layer deposition

Structural, electrical, and optical properties of Ti doped ZnO films fabricated by atomic layer deposition

the charge neutrality of the (100) plane, thereby affecting its surface energy and causing its preferential growth [8]. In addition, the locations of the (100) diffraction peaks shift towards lower diffraction angles as Ti concentration increases, as shown in Figure 2b. To understand this phenomenon, it is worthwhile to notice that the valence of Ti tends to be +4 in the TZO films made by atomic layer deposition. Along the [100] direction, the film layer is composed of the line of Zn 2+ ions or the line of O 2− . If Ti 4+ ions take the place of Zn 2+ sites, the repulsive force in this direction would increase because of extra positive charge. This effect can enlarge the interplanar spacing along the [100] direction, thus leading to the ob- served decrease of the diffraction angle.
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New Chemistries and Processing in Atomic and Molecular Layer Deposition of Inorganic and Hybrid Organic-Inorganic Thin Films

New Chemistries and Processing in Atomic and Molecular Layer Deposition of Inorganic and Hybrid Organic-Inorganic Thin Films

To further explore the diffusion effect of AZ and MA, AB films using AZ-MA sequence at 100 °C were deposited. (The details of different precursor combination and sequence is discussed in Figure 5.5.) Film thickness was characterized by SE when various precursor purge times were applied after 50 MLD cycles (Figure 5.3). In the first experiment, the purge time after AZ and MA were equal (red line). Increases in purge time resulted in thinner films. Specifically, purge times of 15 and 120 s for both precursors yielded a film thickness of 110 and 33 nm, respectively. While prolonged purge of 300 s only leads to a film of 2.07 nm. Considering the first AZ and MA pulses usually add mass gains equivalent to two monolayers as shown in Figure 5.2(a), negligible film growth occurred after the initial MLD cycle. This is in agreement with the proposed diffusion theory that the adsorbed precursors are able to diffuse out of the film given sufficient time, resulting in smaller growth rate. The minimal growth with 300 s purge time after 50 AB cycles indicates that there are negligible effective surface chemical reactions between AZ and MA at 100 °C under the MLD conditions. That is, the growth of materials is fully attributed to the subsurface adsorption of precursors AZ and MA, which otherwise does not occur by surface-limiting reactions.
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Application of Conductive Thin Films and Selectively Patterned Metal Oxide Coatings on Fibers by Atomic Layer Deposition.

Application of Conductive Thin Films and Selectively Patterned Metal Oxide Coatings on Fibers by Atomic Layer Deposition.

doping ratio. .......................................................................................................................... 134 Figure 5.13. Conductivity for AZO coated machine and cross direction nylon is plotted as a function of the inverse radius of curvature, to show how the conductivity of the two substrates orientations changes from intially as-deposited (unbent, 0 cm -1 ) to being bent around smaller cylinders, the smallest of which has a radius of curvature of R≈0.29 cm, which corresponds to the furthest right data point on the graph (3.4 cm -1 ). ......................... 135 Figure 5.14. SEM images of the AZO coated MD PA6 fibers from Figure 5.12, after being strained. The samples were not sputter coated prior to imaging. As a result, non-conductive areas appear dark in the image, revealing the location of cracks in the AZO. The formation of cracks upon straining begin to form, then propogate radially around the fiber, at which point the polymer underneath the fracture can continue to stretch until other cracks are created as a result of localized stress in previously uncracked regions. For all strained samples imaged, there appeared fibers with significantly fewer cracks than a neighboring fiber, the difference is likely due to local variability in tensile forces imparted on the induvidual fibers by the nonwoven fiber network. ...................................................................................................... 136 Figure 5.15. (a) An all fiber pressure sensor was fabricated using AZO coated nylon-6 nonwoven mats as electrodes. An electrically insulating polypropylene mat is place between the electrodes, and the three are stitched together using insulating thread. An insulating nonwoven polypropylene layer with hole cut in the center (inset), allows the electrodes to be sewn together without electrical contact, but also permits contact when pressure is applied; (b) current response, R= I on /I off under applied force as described in text; (c) average R values
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Photo-Assisted Atomic Layer Deposition and Chemical Vapor Deposition of Metal and Metal Oxide Thin Films

Photo-Assisted Atomic Layer Deposition and Chemical Vapor Deposition of Metal and Metal Oxide Thin Films

Compounds serving as precursors for thermal CVD can also be utilized in laser driven processes where deposition occurs via pyrolysis at localized hot spots. In photolytic processes, however, film formation is governed by the optical properties of the compound and precursors suitable for thermal CVD may be of no utility for photo-CVD. Determination of the absorption spectrum of a compound is the most vital step when evaluating its applicability for photo-CVD. 30 The precursor candidate should have strong absorption at the wavelengths emitted by the light source in use. As mentioned in the previous section, the absorption behavior of a compound may be significantly different in the gas phase and on the substrate surface. 26 The altered photochemistry of the adsorbed species may arise from surface relaxation or a different decomposition pathway. 27 The extinction coefficient of the compound should also be taken into account since the effectiveness of photo-enhancement increases as a function of absorbed radiation. Absorption properties depend on the bonding in a given compound. Tightly bound σ-electrons require more energy and thus shorter wavelengths for excitation than the less tightly held π-electrons. The absorption of photons must lead to a reaction path that ultimately results in film formation. Precursors having the metal at a low oxidation state are generally favored since the reduction of these compounds to metallic form occurs more readily as opposed to high-valent metal precursors.
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Atomic layer deposition of crystalline molybdenum oxide thin films and phase control by post-deposition annealing

Atomic layer deposition of crystalline molybdenum oxide thin films and phase control by post-deposition annealing

For many of the abovementioned applications, either uniform thin fi lms or nanoparticles with controlled sizes and morphologies are required. Atomic layer deposition (ALD) is an advanced gas phase thin fi lm deposition method, which relies on alternating self- limiting surface reactions. Therefore, ALD is able to coat large areas as well as substrates with complex shapes with a thickness uni- formity unmatched by any other method. ALD also typically de- posits high-quality fi lms at relatively low deposition temperatures. In addition, due to the cyclic nature of ALD, fi lm thickness and doping can be controlled accurately [44 e 46].
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Atomic layer deposition of crystalline molybdenum oxide thin films and phase control by post-deposition annealing

Atomic layer deposition of crystalline molybdenum oxide thin films and phase control by post-deposition annealing

Fig. 2. (a) Illustration of the ellipsometry model used in this work. Growth rates versus (b) MoO 2 (thd) 2 and (c) O 3 pulse lengths. (d) Film thickness versus the number of ALD cycles (inset shows 0e100 cycles). Growth rates extracted from linear fits to the data are indicated. Growth rates versus (e) purge lengths (only total thickness is shown for clarity) and (f) deposition temperature. Unless otherwise noted, 1000 cycles with 1 s MoO 2 (thd) 2 and 3 s O 3 pulses and 1 s purges were applied at 250  C. Fig. 3. Cross-sectional SEM images of a trench structure (aspect ratio 30:1) con- formally coated with a MoO x film. The film was deposited at 250  C using 1 s
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Nano oxide thin films deposited via atomic layer deposition on microchannel plates

Nano oxide thin films deposited via atomic layer deposition on microchannel plates

From the gain and resistance results shown in Figure 11, the film prepared on condition 4 with the highest resist- ance also has one of the lowest gains. This could be caused by saturation of the MCP since the more conductive coatings will take longer to replenish charge. Indeed, the current (or gain) saturation is determined by the ability of pores to recharge and is mostly governed by the resistance of the conductive layer. Although electron scrubbing process varied substantially, the output currents for con- ventional MCP are exceeding 5% ~ 6% than strip currents when gain saturation appears, and for ALD-MCP, Beaulieu et al. observed that the gain saturation appeared at output currents equal to approximately 10% to 30% of strip cur- rents [24]. And we consider that gain saturation of MCP with more conductive coatings appeared is a possible rea- son for the results of condition 4 shown in Figure 11. But the current jitter phenomenon shown below in Figure 12 is maybe not only related with gain saturation but also re- lated with other reasons like Fermi level difference of ma- terials and varied resistance coefficient of nano-oxide thin films that will be elucidated by further studies.
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Chemical Protective Metal-Organic Framework Thin Films on Fiber Systems Driven by Atomic Layer Deposition.

Chemical Protective Metal-Organic Framework Thin Films on Fiber Systems Driven by Atomic Layer Deposition.

due to polar amine functional groups. 24 To promote the interaction between the MOF and the substrate, we introduced atomic layer deposition (ALD) of metal oxides to impart surface hydroxyl groups onto the inert PP. 25 A supramolecular complex comprised of β-cyclodextrin (β-CD) and cetyltrimethylammonium bromide (CTAB) was used as a self-assembly agent. The hydroxyl units on the cylindrical β-CD and cationic head groups on the linear CTAB molecules lead to a host−guest self-assembly interaction and bind to polar surfaces (including both the MOF and the modified PP) via van der Waals, electrostatic interactions, and hydrogen bonding. 26 −28 The modified surfaces then readily bind to each other at room temperature, leading to dense MOF assembly on the PP. Furthermore, the β-CD and CTAB surface assembly agents work to minimize MOF crystal agglomeration in solution, thereby enabling high mass-loading, conformal coverage, and physically robust surface-attachment of UiO-66-NH 2 crystals. To the best of our knowledge,
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The impact of thickness and thermal annealing on refractive index for aluminum oxide thin films deposited by atomic layer deposition

The impact of thickness and thermal annealing on refractive index for aluminum oxide thin films deposited by atomic layer deposition

caused the anomaly changing trend of refractive index. And the refractive index becomes higher after 900°C an- nealing, which is contributed by vacancy filling induced higher dielectric polarization. The revolution of optical constant will affect other properties of Al 2 O 3 thin films

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Surface Passivation of Silicon Using HfO2 Thin Films Deposited by Remote Plasma Atomic Layer Deposition System

Surface Passivation of Silicon Using HfO2 Thin Films Deposited by Remote Plasma Atomic Layer Deposition System

High-quality surface passivation is very important for a range of crystalline silicon (c-Si)-based electronic devices, and especially for high-efficiency c-Si solar cells. As the need for lower-cost silicon solar cells increases, since Si material has a rather high cost, thinner Si substrates are required. Therefore, their surface/volume ratio of such substrates and the contribution of their surfaces to the overall performance are increasing. Trad- itional surface passivation for Si involves the formation of a thin silicon dioxide (SiO 2 ) layer. However, this

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The effect of film thickness on the gas sensing properties of ultra thin TiO2 films deposited by atomic layer deposition

The effect of film thickness on the gas sensing properties of ultra thin TiO2 films deposited by atomic layer deposition

X-ray Diffraction (XRD) measurements gave no intense peaks for the 10 nm film, which was likely because the film was too thin to produce significant diffraction. This is consistent with the appearance of a broad background peak attributed to break-through to the glass substrate. The 50 nm film, however, showed the presence of peaks attributable to anatase (Figure 8), with the (101) reflection being the most intense (PDF reference number PDF 01-071-1166). As the film thickness increases further the relative peak intensities of the (101) and (200) reflections increased compared to the 50 nm film and the (103), (004), (112), (105) and (211) reflections became more apparent. It has previously been suggested that initially, when the film thickness is low, an amorphous/poorly crystalline layer forms on the surface of the substrate and it is only after subsequent growth that the nucleation sites start to coalesce and form a denser film and become more crystalline [20]. This is consistent with the findings from ellipsometry, where the measured refractive index increased with increasing film thickness. The crystallite size for the 50 nm film was calculated at ~40 nm using the Sherrer equation [24], comparable to the grain size observed using AFM, suggesting that the film consists of a single layer of separated crystallites.
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The Effect of Film Thickness on the Gas Sensing Properties of Ultra-Thin TiO2 Films Deposited by Atomic Layer Deposition

The Effect of Film Thickness on the Gas Sensing Properties of Ultra-Thin TiO2 Films Deposited by Atomic Layer Deposition

To keep the operating temperature constant during the gas sensing performance evaluation, the heater calibration of the TiO 2 coated sensor substrates was performed using a digital pyrom[r]

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Atomic Layer Deposition of Crystalline MoS2 Thin Films : New Molybdenum Precursor for Low-Temperature Film Growth

Atomic Layer Deposition of Crystalline MoS2 Thin Films : New Molybdenum Precursor for Low-Temperature Film Growth

substrate. All of the films were deposited at 300 C. Si and 90 nm SiO 2 /Si substrates were used for XRD and Raman measurements, respectively. We also explored how the deposition temperature affects film crystallinity. As noted earlier, self-limiting growth seemed to occur between 250 and 325 C. The crystallinity of the deposited films seemed to improve with increasing deposition temperature, based on SEM images (Figure 5a) and X-ray diffractograms (Figure 5b). Although a clear increase in grain size was evident at 350 C, and especially at 400 C, these films were not deposited under pure ALD conditions. The film deposited at 400 C consisted of thin flakes standing up from the substrate with a length of approximately 100 nm, for a nominal film thickness of about 20 nm. Deposition of highly crystalline MoS 2 films by ALD appears to call for more thermally
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Characterization of TiO2, ZnO, and TiO2/ZnO thin films prepared by 
		sol gel method

Characterization of TiO2, ZnO, and TiO2/ZnO thin films prepared by sol gel method

(AFM). In this study, the effect of temperature show difference results of single layer and bilayer thin films. The result of XRD shows when the temperature increase, the thin films provide a good crystallization phase in which the structure of the diffraction peaks higher. From the AFM analysis, the surface roughness and the grain size increases as the temperature increase. Based on the characterization was carried out, the increase in temperature has influenced the distribution on the phase structure. The intensity of nanostructure thin films and also the smooth and compacted surface roughness were controlled by the temperature.
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Atomic layer deposition for fabrication of HfO2/Al2O3 thin films with high laser induced damage thresholds

Atomic layer deposition for fabrication of HfO2/Al2O3 thin films with high laser induced damage thresholds

Previous research on the laser damage resistance of thin films deposited by atomic layer deposition (ALD) is rare. In this work, the ALD process for thin film generation was investigated using different process parameters such as various precursor types and pulse duration. The laser-induced damage threshold (LIDT) was measured as a key property for thin films used as laser system components. Reasons for film damaged were also investigated. The LIDTs for thin films deposited by improved process parameters reached a higher level than previously measured. Specifically, the LIDT of the Al 2 O 3 thin film reached 40 J/cm
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Optical Properties of Zn(O,S) Thin Films Deposited by RF Sputtering, Atomic Layer Deposition, and Chemical Bath Deposition

Optical Properties of Zn(O,S) Thin Films Deposited by RF Sputtering, Atomic Layer Deposition, and Chemical Bath Deposition

This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof.
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