1. Substrate Preparation 
<ol>
 <li>Cut 1 cm x 1 cm silicon substrates from a Si wafer, Silicon is good for SEM characterization (plane view and cross section).</li>
 <li>Cut 1 cm x 1 cm glass (soda-lime, 1 mm thick), glass is optimal for optical and electrical characterization.</li>
 <li>If contacts are needed on glass substrates, Au contacts can be evaporated in vacuum by using a mask. Deposit 10 nm of Cr as an interlayer to improve adhesion of Au, deposit 50 nm of Au.</li>
 <li>Cut 1 cm x 1 cm pol...

<ol>
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G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transparent+conductors+as+solar+energy+materials:+A+panoramic+review.">Transparent conductors as solar energy materials: A panoramic review.</a> Solar Energy Materials &amp; Solar Cells. 91, 1529 (2007).</li><li>Minami, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transparent+conducting+oxide+semiconductors+for+transparent+electrodes.">Transparent conducting oxide semiconductors for transparent electrodes.</a> Semicond. Sci. Technol. 20, S35 (2005).</li><li>Fortunato, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transparent+Conducting+Oxides+for+Photovoltaics.">Transparent Conducting Oxides for Photovoltaics.</a> MRS Bulletin. 32, 242 (2007).</li><li>Exarhos, G. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Discovery-based+design+of+transparent+conducting+oxide+films.">Discovery-based design of transparent conducting oxide films.</a> Thin Solid Films. 515, 7025 (2007).</li><li>Gondoni, P., Ghidelli, M., Fonzo, F. D. i., Russo, V., Bruno, P., Mart-Rujas, J., Bottani, C. E., Li Bassi, A., Casari, C. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structural+and+functional+properties+of+Al:ZnO+thin+films+grown+by+Pulsed+Laser+Deposition+at+room+temperature.">Structural and functional properties of Al:ZnO thin films grown by Pulsed Laser Deposition at room temperature.</a> Thin Solid Films. 520, 4707-4711 (2012).</li><li>Gondoni, P., Ghidelli, M., Fonzo, F. D. i., Carminati, M., Russo, V., Li Bassi, A., Casari, C. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structure-dependent+optical+and+electrical+transport+properties+of+nanostructured+Al-doped+ZnO.">Structure-dependent optical and electrical transport properties of nanostructured Al-doped ZnO.</a> Nanotechnology. 23, 365706 (2012).</li><li>Casari, C. S., Li Bassi, A., Arkin, W. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pulsed+Laser+Deposition+of+Nanostructured+Oxides:+from+Clusters+to+Functional+Films.">Pulsed Laser Deposition of Nanostructured Oxides: from Clusters to Functional Films.</a> Advances in Laser and Optics Research. 7, 65-100 (2012).</li><li>Amoruso, S., Sambri, A., Vitiello, M., Wang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plume+expansion+dynamics+during+laser+ablation+of+manganates+in+oxygen+atmosphere.">Plume expansion dynamics during laser ablation of manganates in oxygen atmosphere.</a> Applied Surface Science. 252, 4712-4716 (2006).</li><li>Uccello, A., Dellasega, D., Perissinotto, S., Lecis, N., Passoni, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanostructured+Rhodium+Films+for+Advanced+Mirrors+Produced+by+Pulsed+Laser+Deposition.">Nanostructured Rhodium Films for Advanced Mirrors Produced by Pulsed Laser Deposition.</a> Journal of Nuclear Materials. , (2013).</li><li>Gondoni, P., Ghidelli, M., Fonzo, F. 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The plasma plume shape is closely related to the ablation process, especially in the presence of a gas; monitoring the plasma plume by visual inspection is important to control the deposition. When depositing a metal oxide by ablating an oxide target, oxygen is needed to support oxygen losses during the ablation process. At lower oxygen background gas pressure, the deposited material may have oxygen vacancies. This effect is reduced by increasing the gas pressure. To separate stoichiometry from morphology gas mixt...

Pulsed Laser Deposition (PLD) employs laser ablation of a solid target which results in the formation of a plasma of ablated species which can be deposited on a substrate to grow a film (see Figure 1) 1. Interaction with a background atmosphere (inert or reactive) can be used to induce homogeneous cluster nucleation in the gas phase (see Figure 2) 2,3. Our strategy for material synthesis by PLD is based on the tuning of material properties in a bottom-up approach by carefully controlling the plasma dynamics generated in the PLD process. Cluster size, kinetic energy and composition can be varied by a proper setting of deposition parameters which affect film growth and result in morphological and structural changes 4,5. By exploiting the method described here we demonstrated, for a number of oxides (e.g. WO3, Ag4O4, Al2O3 and TiO2), the capability to tune morphology, density, porosity, degree of structural order, stoichiometry and phase by modifying the material structure at the nanoscale 6-11. This allows the design of materials for specific applications 12-16. With reference to photovoltaic applications, we synthesized nanostructured TiO2 hierarchically organized by assembling nanoparticles (&lt;10 nm) in a nano- and mesostructure that resembles a 'forest of trees' 13 showing interesting results when employed as photoanodes in dye sensitized solar cells (DSSC) 17. Based on these previous results we describe the protocol for the deposition of Al-doped ZnO (AZO) films as a transparent conducting oxide.
Transparent conducting oxides (TCOs) are high bandgap (&gt;3 eV) materials converted into conductors by heavy doping, displaying resistivity &lt;10-3 ohm-cm and more than 80% optical transmittance in the visible range. They are a key element for many applications such as touch screens and solar cells 18-21 and they are typically grown by different techniques such as sputtering, pulsed laser deposition, chemical vapour deposition, spray pyrolysis and with solution-based chemical methods. Among TCOs, indium-tin-oxide (ITO) has been widely studied for its low resistivity but suffers from the drawback of the high cost and low availability of indium. Research is now moving towards indium-free systems such as F-doped SnO2 (FTO), Al-doped ZnO (AZO) and F-doped ZnO (FZO).
Electrodes capable of providing an intelligent management of the incident light (light trapping) are particularly interesting for photovoltaic applications. To exploit the possibility to scatter visible light via structures and morphologies modulated at a scale comparable to the wavelength of light (e.g. 300-1,000 nm), a good control on the film morphology and on cluster assembly architectures is needed.
In particular we describe how to tune morphology and structure of AZO films. Compact AZO deposited at low pressure (2 Pa oxygen) and at room temperature is characterized by low resistivity (4.5 x 10-4 ohm cm) and visible light transparency (&gt; 90%) which is competitive with AZO deposited at high temperatures, while AZO hierarchical structures are obtained by ablating at O2 pressures above 100 Pa. These structures display a strong light scattering capability with haze factor up to 80% and more 22,23.

<table border="1">
 <tbody>
 <tr>
 <td>Name of Reagent/Material</td>
 <td>Company</td>
 <td>Catalog Number</td>
 </tr>
 <tr>
 <td>Pulsed Laser</td>
 <td>Continuum-Quantronix </td>
 <td>Powerlite 8010</td>
 </tr>
 <tr>
 <td>Power meter</td>
 <td>Coherent</td>
 <td>FieldMaxII-TO</td>
 </tr>
 <tr>
 <td>Ion Gun</td>
 <td>Mantis Dep</td>
 <td>RFMax60</td>
 </tr>
 <tr>
 <td>Mass flow controller</td>
 <td>Mks</td>
 <td>2179 &deg;</td>
 </tr>
 <tr>
 <td>Quartz Crystal Microbalance</td>
 <td>Infcon</td>
 <td>XTC/2</td>
 </tr>
 <tr>
 <td>Background gas</td>
 <td>Rivoira-Praxair</td>
 <td>5.0 oxygen</td>
 </tr>
 <tr>
 <td>Target</td>
 <td>Kurt Lesker</td>
 <td>(made on request)</td>
 </tr>
 <tr>
 <td>Isopropanol</td>
 <td>Sigma Aldrich</td>
 <td>190764-2L</td>
 </tr>
 <tr>
 <td>Source meter</td>
 <td>Keithley</td>
 <td>K2400</td>
 </tr>
 <tr>
 <td>Magnet Kit</td>
 <td>Ecopia</td>
 <td>0.55T-Kit</td>
 </tr>
 <tr>
 <td>Spectrophotometer</td>
 <td>PerkinElmer</td>
 <td>Lambda 1050</td>
 </tr>
 </tbody>
</table>

fabrication of nano-engineered transparent conducting oxides by pulsed laser deposition

Nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas allows the deposition of metal oxides with tunable morphology, structure, density and stoichiometry by a proper control of the plasma plume expansion dynamics. Such versatility can be exploited to produce nanostructured films from compact and dense to nanoporous characterized by a hierarchical assembly of nano-sized clusters. In particular we describe the detailed methodology to fabricate two types of Al-doped ZnO (AZO) films as transparent electrodes in photovoltaic devices: 1) at low O2 pressure, compact films with electrical conductivity and optical transparency close to the state of the art transparent conducting oxides (TCO) can be deposited at room temperature, to be compatible with thermally sensitive materials such as polymers used in organic photovoltaics (OPVs); 2) highly light scattering hierarchical structures resembling a forest of nano-trees are produced at higher pressures. Such structures show high Haze factor (&gt;80%) and may be exploited to enhance the light trapping capability. The method here described for AZO films can be applied to other metal oxides relevant for technological applications such as TiO2, Al2O3, WO3 and Ag4O4.

The deposition of AZO by PLD in oxygen atmosphere produces compact transparent conducting films at low background gas pressure (i.e. 2 Pa) and mesoporous forest-like structures constituted by hierarchically assembled clusters at high pressures (i.e. 160 Pa). The material is constituted by nanocrystalline domains whose size is maximum (30 nm) at 2 Pa 22.
Due to collisions between the ablated species and the background gas, the shape and length of the plasma p...

Watch this Scientific Journal Video about Fabrication of Nano-engineered Transparent Conducting Oxides by Pulsed Laser Deposition at JoVE.com

Fabrication of Nano-engineered Transparent Conducting Oxides by Pulsed Laser Deposition

We describe the experimental method to deposit nanostructured oxide thin films by nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas. By using this method Al-doped ZnO (AZO) films, from compact to hierarchically structured as nano-tree forests, can be deposited.

Nanosecond Pulsed  Laser Deposition (PLD) in the presence of a background gas allows the deposition  of metal oxides with tunable morphology, structure, ...

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15.4K visualizações.  Politecnico di Milano. Descreve-se o método experimental para depositar finas películas de óxidos nanoestruturados por nanossegundo deposição por laser pulsado (PLD), na presença de um gás de fundo. Ao usar esse método Al-dopados ZnO (AZO) filmes, de compacto para hierarquicamente estruturado como nano-árvores de florestas, pode ser depositado.