skip to main content

Attention:

The NSF Public Access Repository (NSF-PAR) system and access will be unavailable from 11:00 PM ET on Friday, November 15 until 2:00 AM ET on Saturday, November 16 due to maintenance. We apologize for the inconvenience.


Title: Single-beam ion source enhanced growth of transparent conductive thin films
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.  more » « less
Award ID(s):
1917577
NSF-PAR ID:
10408455
Author(s) / Creator(s):
; ; ; ; ; ; ;
Date Published:
Journal Name:
Journal of Physics D: Applied Physics
Volume:
55
Issue:
39
ISSN:
0022-3727
Page Range / eLocation ID:
395202
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract

    Silver thin films have wide-ranging applications in optical coatings and optoelectronic devices. However, their poor wettability to substrates such as glass often leads to an island growth mode, known as the Volmer–Weber mode. This study demonstrates a method that utilizes a low-energy ion beam (IB) treatment in conjunction with magnetron sputtering to fabricate continuous silver films as thin as 6 nm. A single-beam ion source generates low-energy soft ions to establish a nominal 1 nm seed silver layer, which significantly enhances the wettability of the subsequently deposited silver films, resulting in a continuous film of approximately 6 nm with a resistivity as low as 11.4µΩ.cm. The transmittance spectra of these films were found to be comparable to simulated results, and the standard 100-grid tape test showed a marked improvement in adhesion to glass compared to silver films sputter-deposited without the IB treatment. High-resolution scanning electron microscopy images of the early growth stage indicate that the IB treatment promotes nucleation, while films without the IB treatment tend to form isolated islands. X-ray diffraction patterns indicate that the (111) crystallization is suppressed by the soft IB treatment, while growth of large crystals with (200) orientation is strengthened. This method is a promising approach for the fabrication of silver thin films with improved properties for use in optical coatings and optoelectronics.

     
    more » « less
  2. This chapter presents structural, optical, and magnetic properties of multiferroic LuFeO3 thin films, deposited on single crystal sapphire and YSZ substrates by an RF magnetron sputtering system. Growth temperature and annealing are found to be critical to stabilize hexagonal LuFeO3 thin films. Radio‐Frequency (RF) Magnetron Sputtering is relatively cost effective and one of the most commonly used methods for the deposition of oxides. An RF Magnetron Sputtering offers flexibility in terms of controlling the growth conditions, maintaining the stoichiometry, and a higher deposition rate. When the lattice strain is released due to annealing, the thin film can form bigger granular structures, as observed in the AFM image, by the nucleation process. The inset shows an example of the energy band edge fitting with the direct energy band gap model. 
    more » « less
  3. A single-beam plasma source was developed and used to deposit hydrogenated amorphous carbon (a-C:H) thin films at room temperature. The plasma source was excited by a combined radio frequency and direct current power, which resulted in tunable ion energy over a wide range. The plasma source could effectively dissociate the source hydrocarbon gas and simultaneously emit an ion beam to interact with the deposited film. Using this plasma source and a mixture of argon and C2H2 gas, a-C:H films were deposited at a rate of ∼26 nm/min. The resulting a-C:H film of 1.2 µm thick was still highly transparent with a transmittance of over 90% in the infrared range and an optical bandgap of 2.04 eV. Young’s modulus of the a-C:H film was ∼80 GPa. The combination of the low-temperature high-rate deposition of transparent a-C:H films with moderately high Young’s modulus makes the single-beam plasma source attractive for many coatings applications, especially in which heat-sensitive and soft materials are involved. The single-beam plasma source can be configured into a linear structure, which could be used for large-area coatings.

     
    more » « less
  4. 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. 
    more » « less
  5. The refractory metal iridium has many applications in high performance optical devices due to its high reflectivity into X-ray frequencies, low oxidation rate, and high melting point. Depositing Ir via magnetron sputtering produces high quality thin films, but the chamber pressure and sputter conditions can change Ir film microstructure on the nanoscale. Film microstructure is commonly examined through microscopy of film cross-sections, which is both a destructive characterization method and time consuming. In this work, we have utilized a non-destructive characterization technique, spectroscopic ellipsometry, to correlate the optical properties of the metal films with their structural morphologies, enabling large-scale inspection of optical components or the ability to customize the metal refractive index for the application at hand. The optical properties of Ir thin films deposited at chamber pressures from 10 mTorr to 25 mTorr are reported and compared to microscopy and resistivity results. The measurements were conducted with films deposited both on a bare wafer and on a titanium sublayer.

     
    more » « less