Name: niobium oxide films deposited by reactive sputtering: effect of oxygen flow rate
Uploaded: 2019-09-28T14:30:00
Description: Watch this Scientific Journal Video about Niobium Oxide Films Deposited by Reactive Sputtering: Effect of Oxygen Flow Rate at JoVE.com

The work was supported by Funda&#231;&#227;o de Amparo &#224; Pesquisa do Estado de S&#227;o Paulo (FAPESP), Centro de&#160;Desenvolvimento de Materiais Cer&#226;micos (CDMF- FAPESP&#160;N&#186; 2013/07296-2, 2017/11072-3, 2013/09963-6 and 2017/18916-2). Special thanks to Professor M&#225;ximo Siu Li for PL measurements.

1. Etching and cleaning the substrate
<ol>
	<li>Using a glass cutting system, form 2.5 x 2.5 cm substrates of fluoride thin oxide (FTO).</li>
	<li>Protect part of the substrate surface with a thermal tape leaving 0.5 cm of one side exposed.</li>
	<li>Deposit a small amount of zinc powder (enough to cover the area to be etched) on the top of the exposed FTO and drop concentrated hydrochloric acid (HCl) on the zinc powder slowly until all zinc powder is consumed by the reaction. Immediately after, rinse the substrate wit...

<ol>
	<li>Wasa, K., Kitabatake, M., Adachi, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Thin film materials technology : sputtering of compound materials. , (2004).</li><li>Kelly, P. J., Arnell, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Magnetron+sputtering:+A+review+of+recent+developments+and+applications.">Magnetron sputtering: A review of recent developments and applications.</a> Vacuum. 56, 159-172 (2000).</li><li>Chen, W. -. C., Peng, C. Y., Chang, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Heteroepitaxial+growth+of+TiN+film+on+MgO+(100)+by+reactive+magnetron+sputtering.">Heteroepitaxial growth of TiN film on MgO (100) by reactive magnetron sputtering.</a> Nanoscale Research Letters. 9, 551 (2014).</li><li>Guo, Q. X., 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=Heteroepitaxial+growth+of+gallium+nitride+on+(+1+1+1+)+GaAs+substrates+by+radio+frequency+magnetron+sputtering.">Heteroepitaxial growth of gallium nitride on ( 1 1 1 ) GaAs substrates by radio frequency magnetron sputtering.</a> Journal of Crystal Growth. 239, 1079-1083 (2002).</li><li>Berg, S., Nyberg, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fundamental+understanding+and+modeling+of+reactive+sputtering+processes.">Fundamental understanding and modeling of reactive sputtering processes.</a> Thin Solid films. (476), 215-230 (2005).</li><li>Wong, M. S., Sproul, W. D., Chu, X., Barnett, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reactive+magnetron+sputter+deposition+of+niobium+nitride+films.">Reactive magnetron sputter deposition of niobium nitride films.</a> Journal Vacuum Science &amp; Technology A: Vacuum, Surfaces and Films. 11, 1528-1533 (2002).</li><li>Zoita, C. N., Braic, L., Kiss, A., Braic, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+NbC+coatings+deposited+by+magnetron+sputtering+method.">Characterization of NbC coatings deposited by magnetron sputtering method.</a> Surface and Coatings Technology. 204, 2002-2005 (2010).</li><li>Nico, C., Monteiro, T., Gra&#231;a, M. P. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Niobium+oxides+and+niobates+physical+properties:+Review+and+prospects.">Niobium oxides and niobates physical properties: Review and prospects.</a> Progress in Materials Science. 80, 1-37 (2016).</li><li>Aegerter, M. A., Schmitt, M., Guo, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sol-gel+niobium+pentoxide+coatings:+Applications+to+photovoltaic+energy+conversion+and+electrochromism.">Sol-gel niobium pentoxide coatings: Applications to photovoltaic energy conversion and electrochromism.</a> International Journal of Photoenergy. 4, 1-10 (2002).</li><li>Fernandes, S. L., 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=Hysteresis+dependence+on+CH3NH3PbI3+deposition+method+in+perovskite+solar+cells.">Hysteresis dependence on CH3NH3PbI3 deposition method in perovskite solar cells.</a> Proceedings of SPIE - International Society for Optics and Photonics. 9936, 9936 (2016).</li><li>Fernandes, S. L., 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=Nb2O5hole+blocking+layer+for+hysteresis-free+perovskite+solar+cells.">Nb2O5hole blocking layer for hysteresis-free perovskite solar cells.</a> Materials Letters. 181, 103-107 (2016).</li><li>Hamada, K., Murakami, N., Tsubota, T., Ohno, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Solution-processed+amorphous+niobium+oxide+as+a+novel+electron+collection+layer+for+inverted+polymer+solar+cells.">Solution-processed amorphous niobium oxide as a novel electron collection layer for inverted polymer solar cells.</a> Chemical Physics Letters. 586, 81-84 (2013).</li><li>Aegerter, M. a. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sol-gel+niobium+pentoxide:+A+promising+material+for+electrochromic+coatings,+batteries,+nanocrystalline+solar+cells+and+catalysis.">Sol-gel niobium pentoxide: A promising material for electrochromic coatings, batteries, nanocrystalline solar cells and catalysis.</a> Solar Energy Materials and Solar Cells. 68, 401-422 (2001).</li><li>Rani, R. A., Zoolfakar, A. S., O'Mullane, A. P., Austin, M. W., Kalantar-Zadeh, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thin+films+and+nanostructures+of+niobium+pentoxide:+fundamental+properties,+synthesis+methods+and+applications.">Thin films and nanostructures of niobium pentoxide: fundamental properties, synthesis methods and applications.</a> Journal Materials Chemistry A. 2, 15683-15703 (2014).</li><li>Foroughi-Abari, A., Cadien, K. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Growth,+structure+and+properties+of+sputtered+niobium+oxide+thin+films.">Growth, structure and properties of sputtered niobium oxide thin films.</a> Thin Solid Films. 519, 3068-3073 (2011).</li><li>Numata, Y., 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=Nb-doped+amorphous+titanium+oxide+compact+layer+for+formamidinium-based+high+efficiency+perovskite+solar+cells+by+low-temperature+fabrication.">Nb-doped amorphous titanium oxide compact layer for formamidinium-based high efficiency perovskite solar cells by low-temperature fabrication.</a> Journal Materials Chemistry A. 6, 9583-9591 (2018).</li><li>Gra&#231;a, M. P. F., Meireles, A., Nico, C., Valente, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nb2O5+nanosize+powders+prepared+by+sol-gel+-+Structure,+morphology+and+dielectric+properties.">Nb2O5 nanosize powders prepared by sol-gel - Structure, morphology and dielectric properties.</a> Journal of Alloys and Compounds. 553, 177-182 (2013).</li><li>Kogo, A., Numata, Y., Ikegami, M., Miyasaka, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nb+2+O+5+Blocking+Layer+for+High+Open-circuit+Voltage+Perovskite+Solar+Cells.">Nb 2 O 5 Blocking Layer for High Open-circuit Voltage Perovskite Solar Cells.</a> Chemistry Letters. 44, 829-830 (2015).</li><li>Ueno, S., Fujihara, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+an+Nb2O5+nanolayer+coating+on+ZnO+electrodes+in+dye-sensitized+solar+cells.">Effect of an Nb2O5 nanolayer coating on ZnO electrodes in dye-sensitized solar cells.</a> Electrochimica Acta. 56, 2906-2913 (2011).</li><li>Fernandes, S. L., 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=Exploring+the+Properties+of+Niobium+Oxide+Films+for+Electron+Transport+Layers+in+Perovskite+Solar+Cells.">Exploring the Properties of Niobium Oxide Films for Electron Transport Layers in Perovskite Solar Cells.</a> Frontiers in Chemistry. 7, 1-9 (2019).</li><li>Shirani, A., 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=Tribologically+enhanced+self-healing+of+niobium+oxide+surfaces.">Tribologically enhanced self-healing of niobium oxide surfaces.</a> Surface and Coatings Technology. 364, 273-278 (2014).</li><li>Yan, 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=Nb2O5/TiO2+heterojunctions:+Synthesis+strategy+and+photocatalytic+activity.">Nb2O5/TiO2 heterojunctions: Synthesis strategy and photocatalytic activity.</a> Applied Catalysis B: Environmental. 152 (1), 280-288 (2014).</li></ol>

The niobium oxide films prepared in this work was used as electron transport layer in perovskite solar cells. The most important characteristic required for an electron transport layer is to prevent recombination, blocking holes and transferring efficiently electrons.
In this respect the use of reactive sputtering technique is advantageous since it produces dense and compact films. Also, as already mentioned, compared to sol-gel, anodization, hydrothermal, and chemical vapor deposition synthes...

The sputtering technique is widely used to deposit high-quality films. Its main application is in the semiconductor industry, although it is also used in surface coating for improvement in mechanical properties, and reflective layers1. The main advantage of sputtering is the possibility to deposit different materials over different substrates; the good reproducibility and control over the deposition parameters. The sputtering technique allows deposition of homogeneous films, with good adhesion over large areas and at low-cost when compared with other deposition methods like chemical vapor deposition (CVD), molecular beam epitaxy (MBE) and atomic layer deposition (ALD)1,2. Commonly, semiconductor films deposited by sputtering are amorphous or polycrystalline, however, there are some reports on epitaxial growth by sputtering3,4. Nevertheless, the sputtering process is highly complex and the range of the parameter is wide5, so in order to achieve high-quality films, a good comprehension of the process and parameter optimization is necessary for each material.
There are several articles reporting on the deposition of niobium oxide films by sputtering, as well as niobium nitride6 and niobium carbide7. Among Nb-oxides, niobium pentoxide (Nb2O5) is a transparent, air-stable and water-insoluble material that exhibits extensive polymorphism. It is an n-type semiconductor with band gap values ranging from 3.1 to 5.3 eV, giving these oxides a wide range of applications8,9,10,11,12,13,14,15,16,17,18,19. Nb2O5 has attracted considerable attention as a promising material to be used in perovskite solar cells due to its comparable electron injection efficiency and better chemical stability compared to titanium dioxide (TiO2). In addition, the band gap of Nb2O5 could improve the open-circuit voltage (Voc) of the cells14.
In this work, Nb2O5 was deposited by reactive sputtering under different oxygen flow rates. At low oxygen flow rates, the conductivity of the films were increased without making use of doping, which introduces impurities on the system. These films were used as electron transport layer in perovskite solar cells improving the performance of these cells. It was found that decreasing the amount of oxygen induces the formation of oxygen vacancies, which increases the conductivity of the films leading to solar cells with better efficiency.

<table>
	<tbody>
		<tr>
			<td>2-propanol</td>
			<td>Merck</td>
			<td>67-63-0</td>
			<td>solvent with maximum of 0.005% H2O</td>
		</tr>
		<tr>
			<td>4-tert-butylpyridine</td>
			<td>Sigma Aldrich</td>
			<td>3978-81-2</td>
			<td>chemical with 96% purity</td>
		</tr>
		<tr>
			<td>acetonitrile</td>
			<td>Sigma Aldrich</td>
			<td>75-05-8</td>
			<td>anhydrous solvent , 99.8% purity</td>
		</tr>
		<tr>
			<td>bis(trifluoromethane)sulfonimide lithium salt</td>
			<td>Sigma Aldrich</td>
			<td>90076-65-6</td>
			<td>chemical with &#8805;99.95% purity</td>
		</tr>
		<tr>
			<td>chlorobenzene</td>
			<td>Sigma Aldrich</td>
			<td>108-90-7</td>
			<td>anhydrous solvent , 99.8% purity</td>
		</tr>
		<tr>
			<td>ethanol</td>
			<td>Sigma Aldrich</td>
			<td>200-578-6</td>
			<td>solvent</td>
		</tr>
		<tr>
			<td>Fluorine doped tin oxide (SnO2:F) glass substrate</td>
			<td>Solaronix</td>
			<td>TCO22-7/LI</td>
			<td>substrate to deposit films</td>
		</tr>
		<tr>
			<td>Kaptom tape</td>
			<td>Usinainfo</td>
			<td>04227</td>
			<td>thermal tape used to cover the substrates</td>
		</tr>
		<tr>
			<td>Kurt J Lesker magnetron sputtering system</td>
			<td>Kurt J Lesker</td>
			<td>------</td>
			<td>Sputtering equipment used to deposit compact films</td>
		</tr>
		<tr>
			<td>Lead (II) iodide</td>
			<td>Alfa Aesar</td>
			<td>10101-63-0</td>
			<td>PbI2 salt- 99.998% purity</td>
		</tr>
		<tr>
			<td>methylammonium iodide</td>
			<td>Dyesol</td>
			<td>14965-49-2</td>
			<td>CH3NH3I salt</td>
		</tr>
		<tr>
			<td>N2,N2,N2&#8242;,N2&#8242;,N7,N7,N7&#8242;,N7&#8242;-octakis (4-methoxyphenyl)-9,9&#8242;-spirobi [9H-fluorene]-2,2&#8242;,7,7&#8242;-tetramine</td>
			<td>Sigma Aldrich</td>
			<td>207739-72-8</td>
			<td>Spiro-OMeTAD salt, 99% purity</td>
		</tr>
		<tr>
			<td>Niobium target of 3&#8221;</td>
			<td>CBMM- Brazilian Metallurgy and Mining Company</td>
			<td>------</td>
			<td>niobium sputtering target used in the sputtering system</td>
		</tr>
		<tr>
			<td>N-N dimethylformamide</td>
			<td>Merck</td>
			<td>68-12-2</td>
			<td>solvent with maximum of 0.003% H2O</td>
		</tr>
		<tr>
			<td>TiO2 paste</td>
			<td>Dyesol</td>
			<td>DSL 30NR-D</td>
			<td>titanium dioxide paste</td>
		</tr>
		<tr>
			<td>tris(2-(1H-pyrazol-1-yl)-4-tert-butylpyridine)cobalt(III) tri[bis(trifluoromethane)sulfonimide]</td>
			<td>Dyesol</td>
			<td>329768935</td>
			<td>FK 209 Co(III) TFSL salt</td>
		</tr>
	</tbody>
</table>

niobium oxide films deposited by reactive sputtering: effect of oxygen flow rate

Reactive sputtering is a versatile technique used to form compact films with excellent homogeneity. In addition, it allows easy control over deposition parameters such as gas flow rate that results in changes on composition and thus in the film required properties. In this report, reactive sputtering is used to deposit niobium oxide films. A niobium target is used as metal source and different oxygen flow rates to deposit niobium oxide films. The oxygen flow rate was changed from 3 to 10 sccm. The films deposited under low oxygen flow rates show higher electrical conductivity and provide better perovskite solar cells when used as electron transport layer.

In the sputtering system, the deposition rate is strongly influenced by the oxygen flow rate. The deposition rate decreases when the oxygen flow is increased. Considering the present conditions of the target area used and plasma power, it is observed that from 3 to 4 sccm there is an expressive decrease on the deposition rate, however, when the oxygen is increased from 4 to 10 sccm it becomes less pronounced. In the regime of 3 sccm the deposition rate is 1.1 nm/s, decreasing abruptly to 0.1 nm/s for 10 sccm as seen in <...

Watch this Scientific Journal Video about Niobium Oxide Films Deposited by Reactive Sputtering: Effect of Oxygen Flow Rate at JoVE.com

Niobium Oxide Films Deposited by Reactive Sputtering: Effect of Oxygen Flow Rate

Here, we present a protocol for niobium oxide films deposition by reactive sputtering with different oxygen flow rates for use as an electron transport layer in perovskite solar cells.

Reactive sputtering is a versatile technique used to form compact films with excellent homogeneity. In addition, it allows easy control over deposition ...

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