Nondestructive Spectroscopic Ellipsometry Research Articles

Optical properties of chemical vapor deposition-grown PtSe2 characterized by spectroscopic ellipsometry

PtSe2, an emerging 2D group-10 transition metal dichalcogenide (TMD), has aroused significant attention recently due to its intriguing physical properties. Here, the optical properties of chemical vapor deposition-grown PtSe2 films with different thicknesses were characterized with nondestructive spectroscopic ellipsometry and Fourier transform infrared spectroscopy. The polarized optical microscopy reveals the isotropic in-plane optical response of the continuous PtSe2 films in a scale size of at least as small as 143 × 108 µm2. The electrical transport characterization and UV-mid infrared absorption spectra reveal the coexistence of both semiconducting and metallic contents in these PtSe2 films, making PtSe2 quite different among the 2D material family. The effective refractive index (n) and the extinction coefficient (k) over a spectra range of 360–1700 nm were obtained. In contrast to other TMDs, the values of n and k of PtSe2 were found to have a strong dependence on the thickness and they decrease as the reduction of thickness. This work is conducive to provide vital parameters for further study on PtSe2 and could facilitate its application in optoelectronic devices.

Non-destructive characterization of corroded glass surfaces by spectroscopic ellipsometry

Characterization of the alteration layers that form on glass surfaces during corrosion processes provides valuable information on both the mechanisms and rate of glass alteration. In recent years, state-of-the-art materials and surface characterization techniques have been employed to study various aspects of the alteration layers that result from corrosion. In most cases, these techniques are destructive and thus can only be employed at the end of the corrosion experiment. Here, we show that the alteration layers can be investigated by non-destructive spectroscopic ellipsometry (SE), which provides pertinent information on alteration layer thickness, morphology, and, through correlation of the index of refraction, porosity. SE measurements of silicate glass coupons altered in aqueous solutions of pH3, 5, 7, 9, and 11 at 90°C for 7days are compared to cross-sectional secondary electron microscopy images. In most cases, quantitative agreement of the alteration layer thickness is obtained. The fractional porosity calculated from the index of refraction is lower than the porosity calculated from elemental analysis of the aqueous solutions, indicating that the alteration layer has compacted during corrosion or the subsequent supercritical CO2 drying process. These results confirm the utility of performing non-destructive SE measurements on corroded glass surfaces.

Insights on the Optical Properties of Poly(3,4-Ethylenedioxythiophene):Poly(styrenesulfonate) Formulations by Optical Metrology.

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is among the most widely used polymers that are used as printed transparent electrodes for flexible Organic Electronic (OE) devices, such as Organic Photovoltaics (OPVs). The understanding of their optical properties and the correlation of the optical properties with their electronic properties and metallic-like behavior can lead to the optimization of their functionality as transparent electrodes in multilayer OE device architectures. In this work, we study the optical properties of different PEDOT:PSS formulations by non-destructive Spectroscopic Ellipsometry (SE), from the infrared to the far ultraviolet spectral regions. The optical response of PEDOT:PSS includes an intense optical absorption originated from the conductive part (PEDOT) at lower photon energies, whereas the electronic transition energies of the non-conductive PSS part have been measured at higher photon energies. Based on the different PEDOT:PSS formulations, the optical investigation revealed significant information on the relative contribution of conductive PEDOT and insulating PSS parts of the PEDOT:PSS formulation in the overall optical response, which can strongly impact the final device functionality and its optical transparency.

Optical characterization of the PtSi/Si by using spectroscopic ellipsometry

We report optical characterization of PtSi films for thermoelectric device applications by nondestructive spectroscopic ellipsometry (SE). Pt monolayer and Pt-Si multilayer which consists of 3 pairs of Pt and Si layers were deposited on p-doped-silicon substrates by sputtering method and then rapid annealing process was done to form PtSi films through intermixing of Pt and Si atoms at the interface. Pseudodielectric function data <{\epsilon}> = <{\epsilon}1> + i<{\epsilon}2> of the PtSi/Si samples were obtained from 1.12 to 6.52 eV by using spectroscopic ellipsometry. Employing Tauc-Lorentz and Drude models, the dielectric function ({\epsilon}) of PtSi films were determined. We found that the composition ratio of Pt:Si is nearly 1:1 for PtSi monolayer and we observed transitions between occupied and unoccupied states in Pt 5d states. We also observed formation of PtSi layers in Pt-Si multilayer sample. The SE results were confirmed by the transmission electron microscopy and energy dispersive X-ray spectroscopy.

Non-destructive optical characterization of phase separation in bulk heterojunction organic photovoltaic cells

The dithiophene donor–acceptor copolymers that are bridged either with carbon (C-PCPDTBT) or silicon atoms (Si-PCPDTBT) belong to a promising family of materials for use in photoactive layers for organic photovoltaic cells (OPVs). In this work, we implement the non-destructive Spectroscopic Ellipsometry technique in the near infrared to the far ultraviolet spectral region in combination with advanced theoretical modeling to investigate the vertical distribution of the C-PCPDTBT and Si-PCPDTBT polymer and fullerene ([6,6]-phenyl C71-butyric acid methyl ester – PC70BM) phases in the blend, as well as the effect of the polymer-to-fullerene ratio on the distribution mechanism. It was found that the C-PCPDTBT:PC70BM blends have donor-enriched top regions and acceptor-enriched bottom regions, whereas the donor and acceptor phases are more homogeneously intermixed in the Si-PCPDTBT:PC70BM blends. We suggest that the chemical incompatibility of the two phases as expressed by the difference in their surface energy, may be a key element in promoting the segregation of the lower surface phase to the top region of the photoactive layer. We found that the increase of the photoactive layer thickness reduces the polymer enrichment at the cathode, producing a more homogeneous phase distribution of donor and acceptor in the bulk that leads to the increase of the OPV efficiency.

Monitoring Technological Conditions for Preparing DLC Films in Supersonic Flow of Hydrocarbon Plasma

Properties of diamond-like carbon films deposited by a new method in a supersonic flow of hydrocarbon plasma generated by a disk-type magneto-hydro-dynamic accelerator were studied. Two methods are used for optical and structural characterization of diamond-like carbon films: nondestructive spectroscopic ellipsometry and Raman spectroscopy.

Optical properties and morphology of diamond-like films obtained in a supersonic flow of a hydrocarbon plasma

A possibility of using a new method of film synthesis in a supersonic flow of a hydrocarbon plasma generated by a disk-type magnetohydrodynamic accelerator is demonstrated. Two methods are used for characterization of diamond-like carbon films: nondestructive spectroscopic ellipsometry and atomic-force microscopy.

EUV interferometric lithography and structural characterization of an EUV diffraction grating with nondestructive spectroscopic ellipsometry

In this study, we constructed an exposure platform to perform extreme ultraviolet interferometric lithography (EUVIL) exposure. This platform can be used to expose 1D and 2D gratings, simulating the line/space and contact/hole patterns, respectively. A transmission grating and an achromatic setup were utilized in the exposure. A simple and nondestructive optical characterization approach based on spectroscopic ellipsometry was proposed to characterize the structure of an EUV transmission grating. The optical behavior of a grating was analyzed by rigorous coupled-wave analysis (RCWA). The preliminary exposure results were obtained using the constructed exposure platform.

Optical properties of amorphous diamond films evaluated by non-destructive spectroscopic ellipsometry

Abstract In order to investigate the regularities between the optical properties and the deposition conditions, the optical constants of amorphous diamond films deposited at the different substrate bias with the filtered cathodic vacuum arc technology have been measured by spectroscopic ellipsometry. It has been found that the refractive index and the optical gap of the films firstly increase and then decrease with the enhancing bias and there are respectively the maximal values when the negative bias is 80 V. However, the extinction coefficient of the films firstly minishes and then rises with the adding bias and there is the minimal value when the negative bias is also 80 V. The extinction coefficient gradually drops down with the increasing wavelength of incident light and nearly approaches to zero in the infrared band. Moreover, the adjustable scopes of refractive index and extinction coefficient changed by the substrate bias deflate little by little with the adding wavelength of incident light.

Spectro-ellipsometric Studies of Amorphization and Thermal Annealing in Ion-implanted Silicon

The damage profiles in the P+, BF2+, As+ and B+ ion-implanted silicon specimens are investigated using the nondestructive spectroscopic ellipsometry (SE) technique. The effective dielectric functions of the damaged layers are calculated using the Bruggeman's effective medium approximation, assuming that the damaged layer can be optically represented by the mixture of crystalline and amorphous silicon. By selectively using either the dielectric function of implanted amorphous silicon, or that of the relaxed amorphous silicon as the reference data for the amorphous silicon, we have improved the accuracy in modeling. The model parameters regarding the damaged layer thickness and the degree of amorphization are found to depend on implanting ion species, implantation energies, and total doses. Also, the implantation induced damage profiles are computer simulated and compared with the SE results. When annealed at lower temperatures, implanted amorphous silicon turns into the relaxed amorphous silicon and starts to recrystallize from the interface of the c-Si side due to solid-phase epitaxial growth. At annealing temperatures higher than 600°C, relaxed amorphous layers become crystalline silicon.