AVS 66th International Symposium & Exhibition
    Thin Films Division Tuesday Sessions
       Session TF+AP-TuM

Paper TF+AP-TuM10
Reaction Pathways in Photolytic CVD of Platinum on Organic Thin Films

Tuesday, October 22, 2019, 11:00 am, Room A124-125

Session: ALD and CVD: Precursors and Process Development
Presenter: Bryan G. Salazar, University of Texas at Dallas
Authors: B.G. Salazar, University of Texas at Dallas
H. Liu, University of Florida
L. McElwee-White, University of Florida
A.V. Walker, University of Texas at Dallas
Correspondent: Click to Email
Chemical vapor deposition (CVD) is widely used to deposit materials including metals, oxides, and sulfides. However, CVD is generally unsuitable for use on organic substrates because it often requires high temperatures (> 200 °C). In this work we investigate photolysis as an alternative to thermal activation for CVD of metals on organic thin films. To study the role of precursor chemistry on the Pt CVD process we use three different precursors: (COD)Pt(CH3)2, (COD)PtCl(CH3), and (COD)PtCl2. We also investigate the role of substrate functionality on the CVD process using three different self-assembled monolayers (SAMs) with carboxylic acid-, hydroxyl-, and methyl- terminal groups to model organic thin films. Solution-phase photochemistry studies and residual gas analysis indicate that the photolytic activation of (COD)Pt(CH3)2 and (COD)PtCl(CH3) occurs via the loss of a methyl radical, while the (COD)PtCl2 occurs via the loss of a chlorine. Subsequently these radicals abstract ligands from the gas phase precursor and the organic surface leading to the formation of methane, chloromethane, chlorine and ethane. Using X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry (TOF SIMS), we also investigated the reaction pathways involved on the organic surfaces. The data indicates that the deposition is highly dependent on the wavelength of light, the Pt precursor, and the SAM terminal group. Using (COD)Pt(CH3)2, we observe a small amount of Pt deposition on –OH and –COOH terminated SAM surfaces. In TOF SIMS we observe Pt- and O- containing ions indicating that Pt has inserted into the terminal group. Little, or no, deposition is observed on the –CH3 terminated SAMs. In agreement with previous studies, the data also shows that the neutral polyhapto ligand, COD, is difficult to remove; there are Pt- and COD- containing species present on the surface. Further, the data indicates that there is some SAM decomposition during the deposition. In contrast, for (COD)PtCl(CH3) and (COD)PtCl2 little, or no, Pt deposition is observed and the data indicates that the SAM layers decompose to form polyaromatic hydrocarbons. The damage appears to be caused by the formation of chlorine radicals during the photolysis, which can penetrate through and react with the SAM. In contrast, the methyl radical is larger leading to less SAM damage because it cannot penetrate through the SAM layer. These studies provide insight into the reaction pathways involved in photolytic CVD and the role of radicals in the subsequent deposition and interaction with organic layers. Such studies therefore aid in the rational design of photolytic CVD on organic substrates.