Abstract A single-beam ion source was developed and used in combination with magnetron sputtering to modulate the film microstructure. The ion source emits a single beam of ions that interact with the deposited film and simultaneously enhances the magnetron discharge. The magnetron voltage can be adjusted over a wide range, from approximately 240 to 130 V, as the voltage of the ion source varies from 0 to 150 V, while the magnetron current increases accordingly. The low-voltage high-current magnetron discharge enables a ‘soft sputtering mode’, which is beneficial for thin-film growth. Indium tin oxide (ITO) thin films were deposited at room temperature using a combined single-beam ion source and magnetron sputtering. The ion beam resulted in the formation of polycrystalline ITO thin films with significantly reduced resistivity and surface roughness. Single-beam ion-source-enhanced magnetron sputtering has many potential applications in which low-temperature growth of thin films is required, such as coatings for organic solar cells.
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Development of Indium-tin Oxide Thin Films on PAMAM Dendrimer Layers for Perovskite Solar Cells Application
Despite the dramatic progress that has been made in the power-conversion
efficiency (PCE) of perovskite solar cells (PVSCs), there are still many obstacles to be
overcome before these devices can be economically competitive in the photovoltaics
market. One of the major hurdles in the commercialization of PVSCs is low stability,
which severely limits the effective lifetime of the devices. One of the approaches
to achieving higher stability and lifetime of PVSCs is improvement of PVSC film
quality. In this paper, we have employed a PAMAM dendrimer layer to reduce the
surface roughness of sputter-deposited indium-tin oxide (ITO) films, which were
then used in the fabrication of PVSCs. A PAMAM-8 dendrimer layer was deposited
by dip-coating the substrates in 25 mL of a 1 μMPAMAM-8 ethanol solution before
ITOdeposition. X-ray refractivity (XRR)was used to verify the PAMAMlayer on the
substrate. ITOfilms of 150 nm thicknesswere then deposited onto the PAMAMlayer
using DC magnetron reactive sputtering. The surface roughness, sheet resistance,
and transmissivity of the ITO films were optimized by varying the parameters of
the sputtering process. Atomic force microscopy (AFM) was used to measure the
surface roughness of the ITO films with and without PAMAM dendrimer layer. A
root-mean-square (RMS) film roughness of 1.6 nm, sheet resistance of 21 /ϒ,
and transmissivity of > 91% at a wavelength of 400–700 nm were obtained after
optimization.
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- Award ID(s):
- 2053954
- NSF-PAR ID:
- 10413859
- Date Published:
- Journal Name:
- Energy Technology 2023
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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The use of flashlamp annealing as a low-temperature alternative or supplement to thermal annealing is investigated. Flashlamp annealing and thermal annealing were conducted on 100 nm thick indium tin oxide (ITO) films deposited on glass to compare the properties of films under different annealing methods. The ITO samples had an average initial sheet resistance of 50 Ω/sq. After flashlamp annealing, the sheet resistance was reduced to 33 Ω/sq only, while by thermal annealing at 210 °C for 30 min, a sheet resistance of 29 Ω/sq was achieved. Using a combination of flashlamp annealing and thermal annealing at 155 °C for 5 min, a sheet resistance of 29 Ω/sq was achieved. X-ray diffraction analysis confirmed that flashlamp annealing can be used to crystallize ITO. Flashlamp annealing allows for low-temperature crystallization of ITO on a time scale of 1–3 min. Through electrical and optical characterizations, it was determined that flashlamp annealing can achieve similar electrical and optical properties as thermal annealing. Flashlamp offers the method of low-temperature annealing, which is particularly suitable for temperature sensitive substrates.
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Atomic layer deposition (ALD) of ruthenium (Ru) is being investigated for next generation interconnects and conducting liners for copper metallization. However, integration of ALD Ru with diffusion barrier refractory metal nitrides, such as tantalum nitride (TaN), continues to be a challenge due to its slow nucleation rates. Here, we demonstrate that an ultraviolet-ozone (UV-O3) pretreatment of TaN leads to an oxidized surface that favorably alters the deposition characteristics of ALD Ru from islandlike to layer-by-layer growth. The film morphology and properties are evaluated via spectroscopic ellipsometry, atomic force microscopy, electrical sheet resistance measurements, and thermoreflectance. We report a 1.83 nm continuous Ru film with a roughness of 0.19 nm and a sheet resistance of 10.8 KΩ/□. The interface chemistry between TaN and Ru is studied by x-ray photoelectron spectroscopy. It is shown that UV-O3 pretreatment, while oxidizing TaN, enhances Ru film nucleation and limits further oxidation of the underlying TaN during ALD. An oxygen “gettering” mechanism by TaN is proposed to explain reduced oxygen content in the Ru film and higher electrical conductivity compared to Ru deposited on native-TaN. This work provides a simple and effective approach using UV-O3 pretreatment for obtaining sub-2 nm, smooth, and conducting Ru films on TaN surfaces.
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A transparent indium tin oxide (ITO) contact to bulk n-GaN and n-GaN thin film on c-face sapphire with a specific contact resistivity of 8.06 × 10−4Ω.cm2and 3.71 × 10−4Ω.cm2was measured, respectively. Our studies relied on an RF sputtering system for ITO deposition. We have investigated the formation of the ITO-based contacts on untreated and plasma treated samples. A nonlinear
I–V curve was observed for ITO deposited on untreated samples. On the other hand, anI–V curve with linear behavior was observed for plasma-treated samples, indicating the formation of ohmic contacts. From theC-V measurements, it was observed that there was also an increase in the carrier concentration in plasma treated samples compared to untreated samples. This can be attributed to the removal of surface oxide layer present on the GaN surface, and increase in nitrogen vacancies after SiCl4plasma treatment. In addition, the increase in nitrogen vacancies at the GaN surface can also enhance localized surface/sub-surface carriers, thereby reducing the contact resistance further. -
CdSe is potentially an important material for making tandem junction solar cells with Si and CIGS. Thermodynamic calculations reveal the potential Shockley-Queisser efficiency of such a tandem cell to be in the 45% range. CdSe has the optimum bandgap (1.72eV) for a tandem cell with Si. In this paper, we show that this material system is indeed capable of achieving good electronic properties and reasonable devices can be made in the material. We report on fabricating CdSe materials and heterojunction CdSe solar cells in both superstrate and substrate configurations on FTO/glass and metal substrates. CdSe layer was deposited using thermal evaporation and then was post-treated with CdCl2 to enhance the grainsize and passivate grain boundaries. The device was an ideal heterojunction structure consisting of glass/FTO/n+CdS/ n-CdSe/p organic layer/NiO/ITO. The n+ CdS layer acted to prevent hole recombination at the n+/n interface, and the p organic layer (such as PEDOT:PSS or P3HT) acted to prevent electron recombination at the p+/n interface. The NiO layer was deposited on top of the organic layer to prevent decomposition of the organic layer during ITO deposition. World-record open-circuit voltages exceeding 800 mV and currents of ~15 mA/cm2 were obtained in devices. Detailed material measurements such as SEM revealed large grain sizes approaching 8 micrometer in some of the films after grain enhancement. Optical measurements and QE measurements show the bandgap to be 1.72 eV. XPS measurements showed the CdSe film to be n type. Space-charge limited current was used to measure electron mobilities which were in the range of 1-2 cm2/V-s. Capacitance spectroscopy showed the doping densities to be in the range of a few x 1015/cm3. For substrate devices, the quantum efficiency obtained was in the 90% range.more » « less
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Accepted Manuscript1.0
- Conference Paper:
- The DOI is not currently available.
