Thickness Of Ultrathin Films Research Articles

Determination of photovoltaic parameters of CIGS hetero junction solar cells produced by PLD technique, using SCAPS simulation program

In this study, CIGS ultrathin films of 52 nm, 89 nm, 183 nm and 244 nm thicknesses were grown on a n-Si substrate using PLD technique, then Ag/CIGS/Si/Al hetero-junction solar cells were formed by producing front finger and back contact. While the thickness of CIGS ultrathin film is increased, their grain sizes are also increased, crystal structures are developed and more light is absorbed within the thin film. The straight characteristics of hetero-junctions have been improved while the thicknesses of CIGS ultrathin film is decreased according to J-V characteristics of the hetero-junctions in the darkness. In addition, depending on CIGS ultrathin film thickness, the photovoltaic behavior of CIGS/Si hetero junction solar cells has been studied and interpreted in detail in this article. It can be concluded that CIGS/Si hetero-junction solar cell device produced based on CIGS ultrathin film of 183 nm thickness shows the highest short circuit current density and power conversion efficiency values among other thicknesses, with respect to J-V curve under the illumination (AM 1.5 solar radiation in 80 mW/cm2). Using SCAPS 1-D program, we have been able to successfully simulate CIGS/Si hetero-junction of 183 nm thickness.

Suppressed Chain Entanglement Induced by Thickness of Ultrathin Polystyrene Films

The thickness effect on the relaxation behavior and chain entanglements was investigated for thin polystyrene films. By following the time evolution of the wetting ridge at the surface induced by a...

Uncertainty in the mutual calibration method for the traceable thickness measurement of ultra-thin oxide films

Mutual calibration by a combination of a zero-offset method and a length-unit traceable method has been suggested as a promising approach to determine the traceable thickness of ultra-thin oxide films. However, the measurement uncertainty is somewhat complicated to calculate because the standard uncertainties from the two measurement methods and the linear regression process should be combined. In this study, the mutual calibration method to evaluate the film thickness and uncertainty of ultra-thin oxide films was investigated. The algorithm of the linear regression equation in the mutual calibration method was studied and the uncertainty calculation program for the thickness measurement by mutual calibration was developed. The result will provide an effective and useful guideline to certify the thickness of the ultra-thin oxide film on Si(100) substrate which is used as the gate oxide in the semiconductor devices. The magnitude of the relative expanded uncertainty in the thickness measurement by mutual calibration is in the range from 8.6% to 9.3%.

Dewetting temperatures of prefrozen and grafted layers in solid ultrathin films viewed as melt-memory effects

Undercooled phase exists behind glass phase with superheated medium-range order between Tg and Tn+ > Tm. The ordered volume fraction stays equal to the percolation threshold F ≅ 0.15 of broken bonds up to Tn+. The difference ΔTg between Tg(bulk) of films with thickness (h > h0) and Tg(h) of ultrathin films of thickness (h < h0) is a linear function of (h-ho). Dense layer with minimum thickness hr is grafted against substrate by isothermal annealing, rinsed to reduce film thickness below hr/F, and finally dewetted at Tg. Similar thickness prepared and annealed near Tm and heated above Tm contains residual crystallized layer dewetting at Tn+. The prefrozen layer reproduces the glassy grafted layer in a crystallized state up to Tn+. Melting heat and melting temperature Tm are linear functions of h for h < h0. Prefrozen layers are due to melt-memories leading to new scenarios of crystallization.

An optical Fiber Pressure Sensor With Ultra-Thin Epoxy Film and High Sensitivity Characteristics Based on Blowing Bubble Method

In this paper, an implementation method of high sensitivity thin film fiber optic pressure sensor based on air blowing method is proposed. The utility model is characterized in that a film ultra-thin microbubble structure is firstly formed on the surface of the AB epoxy glue solution by using high-pressure air, and then the film portion of the end portion of the microbubble is transferred to a single-mode fiber head with a hollow glass tube at the top. Finally, a thin film structure fiber Fabry-Perot fiber pressure sensor is formed. The experimental results show that the thickness of the thin film layer at the end of the FP sensor is only 16 μm. Correspondingly, the maximum pressure sensitivity can reach 263.15 pm/kPa. Meanwhile, due to the decrease of film thickness, the sensor's resistance to temperature interference is improved. The prepared fiber Fabry-Perot pressure sensor has the advantages of ultra-thin film thickness, high-pressure sensitivity, low cost and good repeatability. Therefore, it has good application value in high sensitivity pressure and sound wave detection.

Maximum piezoelectricity in a few unit-cell thick planar ZnO – A liquid metal-based synthesis approach

Synthesizing two dimensional (2D) nanomaterials with controlled sub-nanometer thicknesses from non-layered crystals presents both significant challenges and vast opportunities. However, mechanical exfoliation techniques and physical/wet chemical deposition processes are widely disadvantageous for applicability to non-layered structures. Here we have utilized a simple self-limiting approach to prepare large sheets of 2D zinc oxide (ZnO) at the metal-melt/air interface. These ultra-thin sheets demonstrated highly crystalline hexagonal structures. The specific ZnO hexagonal sheet thickness and its interaction with the substrate were found to have a critical impact on d33. This unusual structure resulted in an exceptionally high out of plane piezoelectricity, yielding a giant value of 80 ± 0.8 pm/V at 2.5 unit-cell thickness for d33, which is 5 Zn-O layers in the wurtzite crystal. This out of plane piezoelectricity value is approximately 8 times larger than that of the value for bulk ZnO. Theoretical studies were carried out to elucidate the impact of the thickness and the substrate’s role on the polarization of the layers. The existence of a large piezoelectricity offered by the synergy of the substrate and specific thickness of ultrathin films offers the opportunity for other groups of potentially piezoelectric materials to be explored.

Effect of the surface contamination layer on the thickness measurement of ultra-thin HfO2 films

Mutual calibration by a combination of a zero-offset method (ZOM) and a length-unit traceable method (LTM) was suggested as a method to determine the true thickness of ultra-thin oxide films. Although, medium energy ion scattering spectroscopy (MEIS) and x-ray photoelectron spectroscopy (XPS) were suggested as the ZOMs, the offset value of thickness is affected by the surface contamination layer.In this study, we compared the effect of the surface contamination layer on the thickness measurement of a series of HfO2 films by MEIS and XPS. The surface of the HfO2 films were contaminated by thin carbon layers with the thicknesses from 0.25 nm to 1.30 nm. In MEIS, the variation of the offset value by the surface carbon layer was negligibly small in the range of 0.020 nm. However, it was large in XPS in the range of 0.131 nm. In conclusion, MEIS can be a reliable ZOM to calibrate the offset values in the thickness measurement of ultra-thin oxide films with negligibly small effect of surface contamination.

The Effect of CZTS Ultrathin Film Thickness on the Electrical Characteristic of CZTS/Si Heterojunction Solar Cells in the Darkness and under the Illumination Conditions

In this study, Ag/CZTS/Si/Al heterojunction solar cells were produced depending on some parameters of CZTS ultrathin active film layers grown on a n-Si wafer by PLD technique. CZTS ultrathin films have been produced as a function of the number of laser pulses and then annealed in a tube oven as a function of sulfurization temperature. The crystal structure, the optical and morphological properties of grown&annealed CZTS ultrathin films were examined by XRD, UV-vis spectra, AFM, respectively. The electrical characteristics of CZTS heterojunction solar cell in the darkness, which were investigated by the conventional J-V Method, Cheung Cheung Method and Norde Method. As the thickness of CZTS ultrathin films increased, the forward current of CZTS heterojunctions increased and their ideality factor, serial resistance and barrier height decreased. Also, the efficiency of Ag/CZTS/Si/Al heterojunction solar cells have been examined and characterised as a function of CZTS ultrathin film thickness under the illumination conditions. J-V curves of CZTS heterojunction solar cells were determined under AM 1.5 solar radiation in 80 MW/cm2, all CZTS heterojunction solar cells have exhibited the photovoltaic behaviour. Jsc, Voc, FF, η parameters of Ag/CZTS/Si/Al heterojunction solar cells were measured, interpreted and compared with each other.

Providing of Ultra-Thin Film Thickness Uniformity by Magnetron Sputtering from Two Sources

To achieve high characteristics of single-photon detectors based on WSi thin films it is necessary to provide high film thickness uniformity more than 95%. This paper presents a mathematical modeling of the thickness uniformity of an ultra-thin film formed by magnetron sputtering from two sources, based on an experimentally determined mass flow from a single magnetron, depending on the location of the magnetrons relative to the substrate holder. According to the results of non-uniformity modeling, the requirements for the design and location of the magnetron unit in the chamber were made, which ensured the required non-uniformity of the film thickness of less than 5%.

An improvement on the conversion efficiency of Si/CZTS solar cells by LSPR effect of embedded plasmonic Au nanoparticles

In this work, Au/Si/CZTS/Ag and Au/Si/plasmonic-CZTS/Ag solar cells have been produced using PLD technique. These CZTS solar cells have been produced based on p-type CZTS ultrathin films at different thicknesses of 61 nm, 112 nm and 210 nm which were grown on an n-type Si wafer. Morphologic and crystalline structures as well as optical characteristics of CZTS ultrathin films have been investigated by courtesy of AFM, XRD and UV–vis spectra. J-V characteristics of CZTS solar cells have been obtained under AM 1.5 solar radiation of 80 mW/cm2. It has been observed that Jsc, Voc and η values of CZTS solar cells increase as thickness of CZTS ultrathin films are diagnosed to an optimum thickness. But, CZTS ultrathin films at thickness of 61 nm and 112 nm have low absorption rate and it was observed that absorption rate of CZTS ultrathin films increase dramatically in visible and NIR regions after Au plasmonic nanoparticles were embedded in these CZTS ultrathin films. Furthermore, Jsc and η values of plasmonic CZTS solar cells increase and that increase can be attributed to the transfer of electrons from the plasmonic Au NPs to the conduction band of CZTS semiconductor, the photon absorption of CZTS ultrathin films from visible to NIR region in the wide spectral region, and the increase in the path length of light through in CZTS semiconductor by photon scattering of Au nanoparticles.

Traceable thickness measurement of ultra-thin HfO2 films by medium-energy ion scattering spectroscopy

The thicknesses of a series of ultra-thin HfO2 films were precisely determined by mutual calibration by x-ray photoelectron spectroscopy (XPS) and x-ray reflectometry (XRR) in the recent Consultative Committee for Amount of Substance (CCQM) pilot study P-190. From these well-defined reference film thicknesses, the measurement capability of medium-energy ion scattering spectroscopy (MEIS) for the thickness of HfO2 films was investigated. The film thicknesses determined by MEIS showed a small difference, within 2%, from the reference thicknesses and an offset value of 0.017 nm. The MEIS thicknesses can also be determined by mutual calibration between the transmission electron microscopy (TEM) thicknesses and the MEIS intensity ratios in the region of the substrate and HfO2 film. From linear fitting with the reference thicknesses, the MEIS thicknesses determined by mutual calibration showed a slope value of 1.011 and an offset value of 0.015 nm. As a result, MEIS can be a traceable method to determine the absolute thickness of ultra-thin HfO2 films, and a zero-offset method for application of the mutual calibration method.

Ultrahigh Speed and Broadband Few‐Layer MoTe2/Si 2D–3D Heterojunction‐Based Photodiodes Fabricated by Pulsed Laser Deposition

Abstract2D transition metal dichalcogenides are promising candidates for high‐performance photodetectors. However, the relatively low response speed as well as the complex transfer process hinders their wide applications. Herein, for the first time, the fabrication of a few‐layer MoTe2/Si 2D–3D vertical heterojunction for high‐speed and broadband photodiodes by a pulsed laser deposition technique is reported. Owing to the high junction quality, ultrathin MoTe2 film thickness, and unique vertical n–n heterojunction structure, the photodiode exhibits excellent device performance in terms of a high responsivity of 0.19 A W−1 and a large detectivity of 6.8 × 1013 Jones. The device is also capable of detecting a broadband light with wavelength spanning from 300 to 1800 nm. More importantly, the device possesses an ultrahigh response speed up to 150 ns with a 3‐dB electrical bandwidth approaching 0.12 GHz. This work paves the way toward the fabrication of novel 2D–3D heterojunctions for high‐performance, ultrafast photodetectors.

Controlling inter-sheet-distance in reduced graphene oxide electrodes for highly sensitive electrochemical impedimetric sensing of myoglobin

In order to improve the sensitivity of electrochemical impedance spectroscopy (EIS)-based biosensors, a number of structuring strategies to promote enlarging the electroactive surface area have been recently proposed. However, these approaches have not been applicable to graphene-based electrodes especially due to their ultrathin film thickness (usually <10 nm) and incompatibility with top-down based structuring methods. To challenge this limitation, in this work, we presented a novel means to increase the electroactive surface area and the sensitivity of graphene electrode-based EIS biosensors with obviation of any extrinsic structuring method, such as patterning or pore generation. Instead, graphene oxide (GO) nanosheets functionalized with octadecylamine (ODA) groups to alter the inter-sheet spacing were synthesized and assembled to stacked films. Then, GO films were thermally reduced to form the roughened surface to maximize the electroactive surface area and sensing sensitivity. As a proof of concept demonstration, the sensing performances of rGO electrodes with differential inter-sheet distance were assessed via EIS measurements for the detection of myoglobin (Mb), a representative biomarker of acute myocardial infarction. Taken together, the deliberate control of the extent of interlayer alkylation of stacked GO nanosheets proved to be an effective strategy to produce rGO electrodes with significantly enhanced and/or controlled surface area, giving rise to a remarkably high sensing performance with the detection limit of 2.37 pM concentration of Mb. The presented strategy is simple yet powerful and widely applicable to various types of target molecules, it is therefore expected to provide general platform for biomedical and environmental sensors.

Unusual thickness relaxation of spin-coated polystyrene ultrathin films in the glassy state

Relaxation in the thickness of ultrathin polystyrene films (thickness < 7 nm) on two different solid substrates is investigated at various temperatures by X-ray reflectivity. A thickness relaxation (i.e., ultraslow increase in thickness) is found even at room temperature, at which point any relaxation would hardly be expected because it is lower than the bulk glass transition temperature by at least 70 °C. At room temperature, the thickness relaxation depends on the annealing time and annealing temperature even upon annealing in the rubbery state. The relaxation time of the films formed on a Si–OH substrate is found to be larger than those deposited on a SiO2 substrate, and decreases with increasing temperature. Whereas, the slow increase in thickness also observed at temperatures above Tg, indicates that some of the molecular chains were not in an equilibrium state, which might be due to a persistent, highly strained interfacial layer. Almost no thickness relaxation is observed at temperatures close to the glass transition point Tg, which would suggest that the Tg of ultrathin polystyrene films is determined by the competition between slow relaxation in the interfacial layer and fast relaxation originated in the free surface region. The results demonstrate that the relaxation and glass transition behavior of confined thin films are influenced by residual stress in the substrate interface region.

Production and photovoltaic characterisation of n-Si/p-CZTS heterojunction solar cells based on a CZTS ultrathin active layers

In this study, Au/n-Si/p-CZTS/Ag solar cells have been produced by using PLD technique. Ultrathin CZTS films have been grown on n-Si wafer in different thicknesses depending on number of laser pulses. These ultrathin CZTS films were analysed by XRD, AFM and UV–vis spectra. J–V characteristics of Au/n-Si/p-CZTS/Ag solar cells have been determined based on thickness of ultrathin CZTS films under AM 1.5 solar radiation of 80 mW/cm2. Short circuit current density (mA/cm2), fill factor, open circuit voltage (V) and power conversion efficiency (%) of ultrathin CZTS film solar cells have been determined for device produced in this work. The photovoltaic (PV) characteristics of ultrathin CZTS film solar cells has been discussed in detail in this present article and, as a result, the ideal ultrathin CZTS film solar cell structure having the highest efficiency has been determined and concluded.

Trap Characterization of ALD Al2O3/4H-SiC Metal-Oxide-Semiconductor Interfaces

4H-Silicon carbide (SiC) metal oxide semiconductor field effect transistors (MOSFETs) are enabling high-efficiency power switching applications under high-temperature, and harsh environment conditions because of SiC’s superior physical properties. However, 4H-SiC MOSFETs have a much lower channel conductance due to the trapping of electrons by a high-density of near-interface traps (NITs) at the SiO2/4H-SiC interface [1,2]. These states are spatially located within ~1 nm from the interface and energetically positioned near the conduction band edge of 4H-SiC. Among the many approaches to solve this issue, using atomic layer deposition (ALD) of high k-dielectrics such as Al2O3 is promising. It has been reported that appropriate surface termination of 4H-SiC prior to ALD with hydrogen [3,4] or SiO [5,6] results in improved properties of Al2O3/4H-SiC MOS devices. The SiO termination refers to the insertion of an ultra-thin (~0.7 nm) silicon oxide layer between Al2O3 and 4H-SiC that results in effective channel mobility greater than 250 cm2Vs-1[5, 6]; significantly higher than that obtained by using standard nitrided (NO annealed) [7] SiO2 as the gate dielectric. In this work, we studied the above two surface termination approaches for ALD Al2O3 using electrical characterization and compared to typical thermally grown SiO2. To this end, Si-face n-type 4H-SiC MOS capacitors were fabricated and characterized using the simultaneous high-low frequency capacitance-voltage (CV), current-voltage (IV) and constant capacitance deep level transient spectroscopy (CCDLTS). For H- termination, prior to ALD, samples were etched in H2 at 1600 ◦C followed by annealing in H2 at 1000 ◦C [3, 4]. Following this, ALD was performed at 200 °C using Trimethylaluminum (TMA, Al(CH3)3) as the precursor to deposit ~50 nm of Al2O3. Electrical measurements were carried out after patterning and deposition of Au/Ti gates. In these samples, the interface state density (Dit ~3x1011 cm-2eV-1) near the conduction band edge was comparable to nitrided SiO2 as shown in Fig. 1. In addition, the CCDLTS showed that the typical ‘O1’ and ‘O2’ NITs[8] detected by CCDLTS at 4H-SiC/SiO2 interfaces, with emission activation energies of about 0.15±0.05 eV and 0.39±0.1 eV[4,8] below the 4H-SiC conduction band, were absent at these Al2O3/4H-SiC interfaces (Fig.2), which is extremely encouraging. In the second surface termination approach, ultra-thin (<1 nm) silicon oxide layers were grown thermally before Al2O3 deposition. Different oxidation conditions were employed varying the furnace temperature as 550 ◦C, 600 ◦C and 650 ◦C with 5 min oxidation time. Then, ~40 nm Al2O3 was deposited using the above ALD process and Al gate contacts were formed. Figure 3 shows the typical quasistatic CVs. It can be clearly observed that, with increasing oxidation temperature, the CV curves shift to the left indicating a reduction of negative charges at the interface, consistent with Dit reduction. However as shown in Fig.1, the simultaneous high-low CV reveals much higher Dit for these devices (~1x1013 cm-2eV-1 near the conduction band edge), comparable to typical unpassivated thermal oxides. Previous reports suggest that the ultra-thin oxide film thickness should be about ~0.7 nm to obtain low Dit and high channel mobility [5,6]. Our preliminary XPS analysis suggests that our film thickness is less than this critical value which might be the cause of the higher Dit here. Therefore, within our current results, we observe that surface H-termination prior to ALD of Al2O3 results in significantly lower Dit compared to SiO termination. Further studies with thicker SiO interlayers will be presented at the conference along with chemical bonding results from XPS analysis. Acknowledgments: This work was supported by the II-VI Foundation and US Army Research Lab. The authors thank Drs. Chunkun Jiao and Koushik Ramadoss from Purdue and Drs. Leonard C. Feldman and Ryan Thorpe from Rutgers University for sample fabrication and XPS analysis. [1] T. Kimoto, and J. A. Cooper, Fundamentals of Silicon Carbide Technology, John Wiley, 2014. [2] B. J. Baliga, Fundamentals of power semiconductor devices,1st edn., Springer, US, 2010. [3] T. Seyller, Appl. Phys. A. 85. 4. 371–385, Dec. 2006. [4] I. Jayawardhena, A. Jayawardena, C. Jiao, D. Morisette, and S. Dhar, Materials Science Forum, Proceedings of the 2018 ECSCRM (accepted 2019) [5] T. Hatayama, S. Hino, N. Miura, T. Oomori, and E. Tokumitsu, IEEE Trans. Electron Devices. 55. 8. 2041–2045. 2008. [6] J. Urresti, F. Arith, S. Olsen, N. Wright, and A. O’Neill, IEEE Trans. Electron Devices,66, 4, 1710–1716, Apr. 2019. [7] G. Y. Chung et al., Appl. Phys. Lett. 76. 13. 1713–1715, 2000. [8] A. F. Basile, J. Rozen, J. R. Williams, L. C. Feldman, and P. M. Mooney, J. Appl. Phys., 109, 6, 064514, Mar. 2011. Figure 1

Round‐robin test of medium‐energy ion scattering for quantitative depth profiling of ultrathin HfO2/SiO2/Si films

Medium‐energy ion scattering (MEIS) has been used for quantitative depth profiling with single atomic layer resolution to determine the composition, thickness, and interface structure of ultrathin films and nanoparticles. To assure the consistency of the MEIS analysis, an international round‐robin test (RRT) with nominally 1‐, 3‐, 5‐, and 7‐nm thick HfO2 films was conducted among 12 institutions. The measurements were performed at each participating laboratory under their own conditions, and the collected data were analyzed. For the data analysis, the Moliere potential, the stopping and range of ions in matter (SRIM) 95 and new fitted electronic stopping power and the Chu straggling were used. For analyzing the MEIS data from the magnetic sector and electrostatic analyzers, the neutralization corrections of Marion and Young for 100‐keV H+ and He+ ions and of Armstrong for 400‐ to 500‐keV He+ ions were used. The standard deviations were 5.3% for the composition, 15.3% for the thickness, and 13.3% for the Hf content, and they were improved to 7.3%, 4.5%, and 7.0% by using refitted electronic stopping powers based on the experimental data. Hence, this study suggests that correct electronic stopping powers are critical for quantitative MEIS analysis.

3D porous Ni-Co-P nanosheets on carbon fiber cloth for efficient hydrogen evolution reaction

Besides the urgent demand to improve the electrocatalytic performance of non-noble-metal catalysts, the decrease of catalysts load is also challenging for the radical design of electrocatalysts. In this work, porous Ni-Co-P nanosheet arrays were supported on carbon fiber cloth with an ultrathin film thickness of only ∼62 nm. The cross-linked porous nanosheet structure greatly increases the interface area of electrolytes and catalysts. The superhydrophilic and aerophobic nature is advantageous to interface contact and bubble detachment. These characteristics encourage Ni-Co-P nanosheets to maintain high performance under the condition of low active substance loading. For example, the Ni-Co-P shows superior hydrogen evolution reaction (HER) performances in both alkaline and acidic media, especially in alkaline conditions, which delivers a current density of 10 mA cm−2 at a low overpotential of 57 mV along with the Tafel slope of 69 mV dec−1. This work provides a direction for the development of low-cost and efficient non-noble metal electrocatalysts with ultralow load contents.

Proton Conduction and Oxygen Diffusion in Ultra-Thin Nafion Films in PEM Fuel Cell: How Thin?

The success of PEM fuel cells lies in the design of the cathode where C-supported Pt catalyst is covered by a thin layer of ionomer, allowing easy access of oxygen and protons. The high current densities (1-2 A/cm2) are achieved by the optimization of the thickness of the ionomer between two opposing trends: thinner ionomer allows high oxygen through-plane diffusion, while the in-plane conduction of the protons requires reasonable thickness. Anisotropy is likely to develop in such thin films. The purpose of this work was to investigate the effect of a thinner ionomer layer on the diffusion and conductivity and to establish how thin the ionomer layer can be. Oxygen permeability (DH) and proton conductivity in ultra-thin Nafion films (100-1000nm) were respectively characterized on SiO2 substrate via limiting current measurement and electrochemical impedance spectroscopy for a range of temperature and relative humidity conditions. The transport behavior of these films is comparable to the electrode membrane layer of PEM fuel cells. Values of oxygen permeability were shown to increase with decreasing film thickness. The oxygen diffusion through the gas boundary layer becomes significant only at ultra-thin film thickness. The proton conductivity decreases with decreasing thickness and was disproportional to bulk Nafion behavior. Post-test SEM imaging shows buckling of the thin layer on the silicon wafer between the Pt sites, partially explaining the opposing trends in diffusivity and conductivity as film thickness decreases. Anisotropy exists as the thickness becomes comparable to the size of the aqueous regions of the Nafion ionomer. Measurements of thinner layers (<100nm) were experimentally limited, yet the trends indicate that the thinness of the ionomer in the cathode is limited by its ability to allow proton conductance.

Morphology and effective dielectric functions of ultra-thin gold films

In the present study, a new method for analyzing the dielectric functions in dependence with the thickness of ultra-thin gold films is proposed. The reliability of the method is carefully verified through the correlation of optical properties and structural morphology of gold films at thicknesses around the percolation threshold (from 2 to 20 nm). The optical characterization of deposited films is performed in visible and NIR regions (300-1500 nm) by a spectroscopic ellipsometry along with transmission spectra measurements at normal incidence. Fitting of the ellipsometric data allows one to calculate the effective complex dielectric function of cluster-like and continuous films of different mass-equivalent thickness. Surface morphology of the films is analysed by scanning electron microscopy.