Investigation of the Layered Structure of Polycrystalline Diamond Thin Films Grown by ECR-Assisted CVD by Spectroscopic
- PDF / 218,271 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 99 Downloads / 195 Views
Investigation of the Layered Structure of Polycrystalline Diamond Thin Films Grown by ECR-Assisted CVD by Spectroscopic Phase Modulated Ellipsometry S. Guptaa, B. R. Weinerb, and G. Morellc a Department of Physics, University of Puerto Rico, San Juan, PO Box 23343, PR00931, USA b Department of Chemistry, University of Puerto Rico, San Juan, PO Box 23346, PR00931, USA c Department of Physical Sciences, University of Puerto Rico, San Juan, PO Box 23323, PR00931, USA ABSTRACT Polycrystalline diamond thin films deposited by the electron cyclotron resonance-assisted chemical vapor deposition (ECR-CVD) were investigated using spectroscopic ellipsometry (SE) from the near IR to UV range (830 nm-270 nm). Employing the conventional Bruggeman effective medium approximation (EMA) and linear regression analysis (LRA) to the raw ellipsometry data (ψ(λi), ∆(λi)) provided the details about the film microstructure: (i) the multilayer structure and the ovearall thickness of the films; (ii) the volume fraction of the constituents (sp3 - and sp2 - bonded carbon) and of voids in the bulk layer; (iii) the inhomogeneity of the structure along the growth axis and its variation with the seeding density; and (iv) the surface roughness layer. A simplified three-layer structural model consisting of an interfacial layer, an intermediate (or bulk) layer and the top surface roughness layer has been proposed to simulate the ellipsometry data. The results obtained through ellipsometry modeling such as surface roughness layer and overall film thickness were compared with rms surface roughness from atomic force microscopy (AFM) and profilometry respectively, in order to validate the model employed. The results such as fv and fsp2C for the bulk layer and its behavior with respect to process parameters are discussed. INTRODUCTION Besides being the hardest material known, diamond is transparent from the infrared (IR) to near ultraviolet (UV) region (with an optical bandgap of 5.45 eV) and has very high electron and hole mobilities [1,2]. This combination of superlative properties result in many potential technological applications of diamond, such as optical coatings, wide-band IR transmissive windows, and high-power opto-electronic switching devices to name a few. A great deal of attention is given to the microstructural analysis of the surface and interfaces of the thin films in order to establish structure-property correlation. Among several state-of-the art techniques for optical characterization, spectroscopic ellipsometry (SE) proved to be very influential and advantageous for the last two decades in the thin film structural analysis [3-5]. The ability of ellipsometry to obtain optical data is advantageous in scanning the parameter window for the desired properties. Hereby, we employed ex situ SE for determining the layered structure of polycrystalline diamond thin films deposited by the electron cyclotron resonance-assisted chemical vapor deposition (ECR-CVD) and its microstructure. The complex refractive index of polycrystalline diamond, ñ = n
Data Loading...
