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1. Enhanced Vapor Transmission Barrier Properties via Silicon-Incorporated Diamond-Like Carbon Coating

   https://doi.org/10.3390/polym13203543  

   Riley, Parand R.; Joshi, Pratik; Azizi Machekposhti, Sina; Sachan, Ritesh; Narayan, Jagdish; Narayan, Roger J. (October 2021, Polymers)

   In this study, we describe reducing the moisture vapor transmission through a commercial polymer bag material using a silicon-incorporated diamond-like carbon (Si-DLC) coating that was deposited using plasma-enhanced chemical vapor deposition. The structure of the Si-DLC coating was analyzed using scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, selective area electron diffraction, and electron energy loss spectroscopy. Moisture vapor transmission rate (MVTR) testing was used to understand the moisture transmission barrier properties of Si-DLC-coated polymer bag material; the MVTR values decreased from 10.10 g/m2 24 h for the as-received polymer bag material to 6.31 g/m2 24 h for the Si-DLC-coated polymer bag material. Water stability tests were conducted to understand the resistance of the Si-DLC coatings toward moisture; the results confirmed the stability of Si-DLC coatings in contact with water up to 100 °C for 4 h. A peel-off adhesion test using scotch tape indicated that the good adhesion of the Si-DLC film to the substrate was preserved in contact with water up to 100 °C for 4 h. 

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2. Response of Photoluminescence of H-Terminated and Hydrosilylated Porous Si Powders to Rinsing and Temperature

   https://doi.org/10.3390/surfaces3030027  

   Kolasinski, Kurt; Swanson, Joseph; Roe, Benjamin; Lee, Teresa (September 2020, Surfaces)

   null (Ed.)

   The photoluminescence (PL) response of porous Si has potential applications in a number of sensor and bioimaging techniques. However, many questions still remain regarding how to stabilize and enhance the PL signal, as well as how PL responds to environmental factors. Regenerative electroless etching (ReEtching) was used to produce photoluminescent porous Si directly from Si powder. As etched, the material was H-terminated. The intensity and peak wavelength were greatly affected by the rinsing protocol employed. The highest intensity and bluest PL were obtained when dilute HCl(aq) rinsing was followed by pentane wetting and vacuum oven drying. Roughly half of the hydrogen coverage was replaced with –RCOOH groups by thermal hydrosilylation. Hydrosilylated porous Si exhibited greater stability in aqueous solutions than H-terminated porous Si. Pickling of hydrosilylated porous Si in phosphate buffer was used to increase the PL intensity without significantly shifting the PL wavelength. PL intensity, wavelength and peak shape responded linearly with temperature change in a manner that was specific to the surface termination, which could facilitate the use of these parameters in a differential sensor scheme that exploits the inherent inhomogeneities of porous Si PL response. 

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3. Chemical Structure Analysis of Carbon-Doped Silicon Oxide Thin Films by Plasma-Enhanced Chemical Vapor Deposition of Tetrakis(Trimethylsilyloxy)Silane Precursor

   https://doi.org/10.1115/IMECE2021-72026  

   Comeaux, Jacob; Wirth, William B; Courville, Justin; Luo, Lingyiqian; Yan, Hui; Jang, Seonhee (November 2021, American Society of Mechanical Engineers)

   Abstract Carbon-doped silicon oxide (CDO) thin films as low dielectric constant materials were deposited on both n-type silicon (Si) (100) and indium tin oxide coated polyethylene naphthalate (ITO/PEN) substrates, using the plasma-enhanced chemical vapor deposition of tetrakis(trimethylsilyoxy)silane (TTMSS) precursor. Chemical structures of the CDO films were analyzed by using FTIR (Fourier transformation infrared) spectroscopy and XPS (X-ray photoelectron spectroscopy). The chemical bonds related with hydrocarbon and Si–O were the main characteristics of the CDO films. The prominent peaks from the FTIR spectra included Si–O–Si stretching, Si–CH3 bending, Si–(CH3)x stretching, and CHx stretching modes. XPS spectra composed of the O1s, C1s, and Si2p electron orbitals were used to quantitatively analyze the elemental composition of the CDO films. The growth mechanisms of CDO films were dependent on the substrate type. For the ITO/PEN substrate, the lack of Si atoms on the ITO surface made difficulty in forming initial Si–O bonds, resulting in insufficient Si–O–Si structure. In comparison, the CDO films could grow easily on Si substrates due to pre-existing Si–O bonds on the surface. The chemical structures of the CDO films are expected to affect electrical and mechanical performances. 

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4. Thermoelectric properties of copper chalcogenide alloys deposited via the solution-phase using a thiol–amine solvent mixture

   https://doi.org/10.1039/c6ra15929j  

   Ma, Yuanyu; Vartak, Prathamesh B.; Nagaraj, Prajwal; Wang, Robert Y. (January 2016, RSC Advances)

   There has been a growing interest in solution-phase routes to thermoelectric materials due to the decreased costs and novel device architectures that these methods enable. Many excellent thermoelectric materials are metal chalcogenide semiconductors and the ability to create soluble metal chalcogenide semiconductor precursors using thiol–amine solvent mixtures was recently demonstrated by others. In this paper, we report the first thermoelectric property measurements on metal chalcogenide thin films made in this manner. We create Cu 2−x Se y S 1−y and Ag-doped Cu 2−x Se y S 1−y thin films and study the interrelationship between their composition and room temperature thermoelectric properties. We find that the precursor annealing temperature affects the metal : chalcogen ratio, and leads to charge carrier concentration changes that affect the Seebeck coefficient and electrical conductivity. Increasing the Se : S ratio increases electrical conductivity and decreases the Seebeck coefficient. We also find that incorporating Ag into the Cu 2−x Se y S 1−y film leads to appreciable improvements in thermoelectric performance by increasing the Seebeck coefficient and decreasing thermal conductivity. Overall, we find that the room temperature thermoelectric properties of these solution-processed materials are comparable to measurements on Cu 2−x Se alloys made via conventional thermoelectric material processing methods. Achieving parity between solution-phase processing and conventional processing is an important milestone and demonstrates the promise of this binary solvent approach as a solution-phase route to thermoelectric materials. 

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5. The role of carbon and C-H neutralization in MOCVD β-Ga2O3 using TMGa as precursor

   https://doi.org/10.1063/5.0153626  

   Meng, Lingyu; Bhuiyan, A F; Zhao, Hongping (June 2023, Applied Physics Letters)

   In this Letter, the role of background carbon in metalorganic chemical vapor deposition (MOCVD) β-Ga2O3 growth using trimethylgallium (TMGa) as the Ga precursor was investigated. The quantitative C and H incorporations in MOCVD β-Ga2O3 thin films grown at different growth rates and temperatures were measured via quantitative secondary ion mass spectroscopy (SIMS). The SIMS results revealed both [C] and [H] increase as the TMGa molar flow rate/growth rate increases or growth temperature decreases. The intentional Si incorporation in MOCVD β-Ga2O3 thin films decreases as the growth rate increases or the growth temperature decreases. For films grown at relatively fast growth rates (GRs) (TMGa > 58 μmol/min, GR > 2.8 μm/h) or relatively low temperature (<950 °C), the [C] increases faster than that of the [H]. The experimental results from this study demonstrate the previously predicted theory—H can effectively passivate the compensation effect of C in n-type β-Ga2O3. The extracted net doping concentration from quantitative SIMS {[Si]-([C]-[H])} agrees well with the free carrier concentration measured from Hall measurement. The revealing of the role of C compensation in MOCVD β-Ga2O3 and the effect of H incorporation will provide guidance on designing material synthesis for targeted device applications. 

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