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The experimental study of the static and dynamic femtosecond laser ablation of the multilayer 15x(Ti/Zr)/Si system is reported. The layer-by-layer selective laser ablation mechanism was studied by analysis of the surface morphology and elemental composition in static single pulse irradiation in a range of pulse energy from 10 to 17 $$\upmu $$J. The selective ablations, as number of concentric circles in modified spots are increased with the pulse energy. The boundary between the circles was shown a change in the depth, comparable to the thickness of the individual layers. Changes in the elemental composition at the edges are associated with the removal of the layer by layer. The dynamic multipulse irradiation was observed via the production of lines with laser-induced periodic surface structures (LIPSS) at different laser parameters (scan velocities and laser polarization). The spatial periodicity of the formed LIPSS depends on changes in the effective number of pulses and laser polarization, as well as the nature of the material. For better interpretation of the experimental results, simulations have been conducted to explore the thermal response of the multiple layered structure 15x(Ti/Zr) after static single pulse irradiation.

The influence of deposition and annealing parameters on optical, structural and photocatalytic properties of N-doped titanium-dioxide (TiO2) thin films have been studied. Anatase and anatase-rutile crystalline phase mixture TiO2 thin films were obtained depending on the reactive direct current (DC) sputtering and annealing conditions. Deposition in the nitrogen atmosphere produced N-doped TiO2 thin films with energy gap values shifted towards visible region in comparison with thin TiO2 films deposited without nitrogen in the atmosphere. The role of substitutional and interstitial nitrogen atoms incorporated in obtained crystalline structures during the deposition was shown important and was reflected in the efficiency of photocatalysis. It was found that thin TiO2 films with more substitutional incorporated nitrogen exhibits better photocatalytic properties. These results could be of importance towards achieving controlled synthesis of N-doped TiO2 thin films with desired structural and optical properties, especially with improved photo-activity in the visible part of the solar spectrum.

Ultrafast laser processing with the formation of periodic surface nanostructures on the 15×(Ti/Zr)/Si multilayers is studied in order to the improve cell response. A novel nanocomposite structure in the form of 15x(Ti/Zr)/Si multilayer thin films, with satisfying mechanical properties and moderate biocompatibility, was deposited by ion sputtering on an Si substrate. The multilayer 15×(Ti/Zr)/Si thin films were modified by femtosecond laser pulses in air to induce the following modifications: (i) mixing of components inside of the multilayer structures, (ii) the formation of an ultrathin oxide layer at the surfaces, and (iii) surface nano-texturing with the creation of laser-induced periodic surface structure (LIPSS). The focus of this study was an examination of the novel Ti/Zr multilayer thin films in order to create a surface texture with suitable composition and structure for cell integration. Using the SEM and confocal microscopies of the laser-modified Ti/Zr surfaces with seeded cell culture (NIH 3T3 fibroblasts), it was found that cell adhesion and growth depend on the surface composition and morphological patterns. These results indicated a good proliferation of cells after two and four days with some tendency of the cell orientation along the LIPSSs. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.

The formation of an ordered surface texture with micro and nanometer features on Ti/Zr multilayers is studied for better understanding and improvement of cell integration. Nanocomposite in form 30×(Ti/Zr)/Si thin films was deposited by ion sputtering on Si substrate for biocompatibility investigation. Surface texturing by femtosecond laser processing made it possible to form the laser-induced periodic surface structure (LIPSS) in each laser-written line. At fluence slightly above the ablation threshold, beside the formation of low spatial frequency-LIPSS (LSFL) oriented perpendicular to the direction of the laser polarization, the laser-induced surface oxidation was achieved on the irradiated area. Intermixing between the Ti and Zr layers with the formation of alloy in the sub-surface region was attained during the laser processing. The surface of the Ti/Zr multilayer system with changed composition and topography was used to observe the effect of topography on the survival, adhesion and proliferation of the murine mesenchymal stem cells (MSCs). Confocal and SEM microscopy images showed that cell adhesion and their growth improve on these modified surfaces, with tendency of the cell orientation along of LIPSS in laser-written lines. © 2019 by the authors.

Nanosphere lithography is an effective technique for high throughput fabrication of well-ordered patterns on large areas. This study reports on nanostructuring of silicon samples by means of Ag ions implantation through self-organized polystyrene (PS) masks. The PS nanospheres with a diameter of ∼150 nm were self-assembled in a hexagonal array on top of Si(100) wafers, and then used as a mask for subsequent 60 keV silver ion implantation. Different fluences were applied up to 2 × 1016 ions/cm2 in order to create a distribution of different sizes and densities of buried metal nanoparticles. The surface morphology and the subsurface structures were studied by scanning electron microscopy and cross-sectional transmission electron microscopy, as a function of the mask deformation upon irradiation and the implantation parameters itself. We demonstrate that Ag is implanted into Si only through the mask openings, thus forming a regular array of amorphized regions over the wide area of silicon substrate. These fragments are of similar dimensions of the spheres with widths of about 190 nm and distributed over 60 nm in depth due to the given ion range. At the subsurface region of the implanted fragments, the synthesis of small sized and optically active Ag nanoparticles is clearly observed. The samples show a strong absorption peak in the long-wavelength region from 689 to 745 nm characteristic for surface plasmon resonance excitations, which could be fitted well using the Maxwell-Garnett`s theory. © 2018 Elsevier B.V.

INTRODUCTION: Titanium dioxide (TiO2) thin films showed as promising materials for photocatalytic degradation of pollutants in water under irradiation of UV-light. It is favorable material for photocatalytic processes because of its non-toxicity, high photosensitivity, large band gap and stability. One of the way to increase efficiency of TiO2 thin films is by doping and coating with metals. Metal-doped TiO2 can reduce electron-hole recombination and increase hydroxyl radical concentration on the surface of TiO2, resulting in increase in the photocatalytic activity1. In studies of J.M.Jung at al.1 with Au-buffered TiO2 thin films and V. S. Mohite et al.2 with doped TiO2 thin films showed that this systems have enhanced photocatalytic activity in comparison to pure TiO2 thin films. Also recent study3 showed that Au doped TiO2 thin films are great candidates beside photocatalysis for enhancing visible light water splitting. EXPERIMENTAL STUDY TiO2 and TiO2:Au thin films were obtained by DC magnetron sputtering of Ti target with Ar ions in O2 atmosphere. In the case of doped TiO2 thin films with Au, three different systems were deposited for comparison (fig.1): Buffering Au layer into the TiO2 layer (b), subsurface buffering of Au with island formation of Au on the surface and etching the surface of TiO2 layer by HF and applying Au nanoparticles on the surface. Annealing of the samples was performed in air and N2 atmospheres on 600 °C for better crystallinity and release of defects. For structural analyses XRD, XPS, TEM and SEM methods were used, while for optical characterization UV/Vis method was used. The photo-degradation rate was measured using Rhodamine B which simulated pollutant. Fig. 1: Experimental setup. RESULTS AND DISCUSSION Structural analysis has shown that as deposited films have amorphous-like structures, while post-deposition thermal annealing in air for 3 hours inducted significantly better crystallinity in thin films with anatase phase dominating. S

We report an experimental study of Cr2O3 thin films (60, 300, 350 nm) deposited on silicon and glass substrates using the Balzers Sputtron II System. The structural and optical properties were investigated by means of AFM, XRD, UV-VIS, Raman and infrared spectroscopy, in order to determine the suitability of the as-obtained films as potential active layers in novel differential inorganic photodetectors. AFM measurements revealed that all films are well-deposited, without the presence of any cracks or voids. The crystalline peaks in the XRD spectra belonged to the trigonal Cr2O3 structure. UV-VIS measurements revealed a strong red shift in the absorption maxima with reducing film thickness. IR and Raman spectroscopy show a dependence of the characteristic vibrations on film thickness as well as on the substrate. In conclusion, our results indicate that the Cr2O3 film of 300 nm thickness is so far the most promising candidate as photoactive semiconducting layer in differential photodetectors.

The possibility of interlayer mixing in a Ti/Ta multilayer system, induced by laser irradiation, was the main purpose of these experiments. Ti/Ta multilayer system, consisting of ten alternating Ti and Ta thin films and covered by slightly thicker Ti layer, was deposited on Si (100) wafers to a total thickness of 205 nm. Laser irradiation was performed in air by picoseconds Nd:YAG laser pulses in defocused regime with fluences of 0.057 and 0.11 J cm−2. Laser beam was scanned over the 5 × 5 mm surface area with different steps along y-axes. Structural and compositional characterisation was done by auger electron spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy, and scanning electron microscopy. Laser processing at lower fluence caused only oxidation of the top Ti layer, despite of the number of applied laser pulses. Interlayer mixing was not observed. Application of laser pulses at fluence of 0.11 J cm−2caused partial and/or complete ablation of deposited layers. In partially ablated regions considerable mixing between Ti and Ta films was registered.

Femtosecond laser texturing holds promise for the surface modification of materials, due to a wide application to all materials; the possibility of getting a wide variety of structures with micro- and nano-scaled features; and a fast, repeatable and contactless process. Laser processing is unique method, which allows production of active surface with formation of the desired oxide, creation of nano/micro textures and change wettability of the surface. Due to excellent mechanical properties and moderate biocompatibility, Ti/Zr multi- layer thin films, as novel nanolayered composites were deposited by ion sputtering on Si substrate. Subsequently, the Ti/Zr thin films were irradiated by femtosecond laser pulses in air to induce the following modifications: (i) mixing of components within the thin film structures, (ii) formation of ultrathin oxide layer at the irradiated surfaces, and (iii) structuring of the surface arrays in form of ripple structure. The main focus of this experimental study was examined different surface motives with nano- and micrometre features. For this purpose, the modifications of Ti/Zr multilayers were included forma- tion of spots, lines and surfaces with different pulse energy, scanning speed i.e. number of pulses, z-distance. Laser-induced spots are composed of concentric circles, where the number of circles in individual spots is increased with increasing pulse energy. Maxi- mum depth in the centre of spots and total roughness are gradually rising with pulse energy, but heights between ablated layers in these spots does not match with the thick- ness of layers, but these deviations are not significant. Lines and surfaces were scanned with different scanning rate, the conditions for formation of well-defined LSFL (low spa- tial frequency LIPSS) are determined. The periodic structures at high scanning rate (3 mm/s) are mainly formed on the multilayer thin film. However, the degree of ablation becomes higher at the lowest rate (0.5 mm/s) where

Modification of single and complex nickel-palladium samples by laser processing in the femtosecond time domain was studied. The samples were processed by focused Ti:Sapphire laser beam (Clark CPA-2101) with 775 nm laser wavelength, 2 kHz repetition rate, 200 fs pulse duration. The laser-induced morphological modifications have shown dependence on the applied fluences and number of laser pulses. The formed surface nanostructures on the single NiPd/Si and multilayer 5x(Ni/Pd)/Si systems are compared with individual Ni and Pd thin films. The results show an increase in surface roughness, formation of parallel periodic surface structures, appearance of hydrodynamic features and ablation of surface material. At low number of pulses (less than 10 pulses) and low pulse energies range (not over 1.7 mu J), the two types of laser-induced periodic surface structure (LIPSS) can be observed: low and high spatial frequency LIPSS (HSFL and LSFL). For all samples, the measured LSFL periods were 720 nm for the ripples created solely on thin film surfaces during the single pulse action. In the case of the multi-pulse irradiation, the periodicities of created LSFLs on the all investigated thin films have shown tendency to reduction with increasing of pulse energies. (C) 2016 Elsevier B.V. All rights reserved.

Multilayers consisting of five (Al/Ti) bilayers were deposited on (100) silicon wafers. On top was deposited the Ti layer, aimed at preventing Al from diffusing to the surface upon laser treatment. The total thickness of the thin-film structure was 200 nm. Laser irradiations with Nd:YAG picoseconds laser pulses in the defocused regime were performed in air. Laser beam energy was 4 mJ and laser spot diameter on the sample surface was 3 mm (fluence 0.057 J cm(-2)). The samples were treated with different numbers of laser pulses. Structural characterizations were performed by different analytical methods and nano-hardness was also measured. Laser processing induced layer intermixing, formation of titanium aluminides, oxidation of the surface titanium layer and enhanced surface roughness. Aluminum appears at the sample surface only for the highest density of laser irradiation. Laser processing induces increment of nano-hardness by approximately 20% and decrease of residual Youngs modulus for a few percentages from the starting value of the untreated samples. These results can be interesting toward achieving structures with a selective extent of Al-Ti reactivity in this multilayered system, within the development of biocompatible materials.

Formation of periodic nanostructures on the Ti/5x(Al/Ti)/Si multilayers induced by picosecond laser pulses is studied in order to better understand the formation of a laser-induced periodic surface structure (LIPSS). At fluence slightly below the ablation threshold, the formation of low spatial frequency-LIPSS (LSFL) oriented perpendicular to the direction of the laser polarization is observed on the irradiated area. Prolonged irradiation while scanning results in the formation of a high spatial frequency-LIPSS (HSFL), on top of the LSFLs, creating a co-existence parallel periodic structure. HSFL was oriented parallel to the incident laser polarization. Intermixing between the Al and Ti layers with the formation of Al-Ti intermetallic compounds was achieved during the irradiation. The intermetallic region was formed mostly within the heat affected zone of the sample. Surface segregation of aluminium with partial ablation of the top layer of titanium was followed by the formation of an ultra-thin Al2O3 film on the surface of the multi-layered structure. Published by AIP Publishing.

Metallic biomaterials should exhibit excellent biocompatibility, high corrosion resistance and low elastic modulus which are close to that of human bones. It was shown that in this sence Ti-Ta alloys have considerably better mechanical properties compared to pure titanium or tantalum [1, 2]. The main purpose of these experiments was investigation of possibility to induce interlayer mixing in an Ti/Ta immiscible multilayer system by laser irradiation.The absence of interlayer mixing was previously shown on this system during the Ar+ ion irradiation up to relatively high fluence of 2x1016 ions cm-2 [3]. The system consisted of ten alternate Ti and Ta thin films (~18 nm each) and covered by slightly thicker Ti layer (~27 nm) on the top with the purpose of creating an appropriate porous structure very important for potential biocompatibility [4]. Structure was deposited on Si (100) wafers to a total thickness of 205 nm. Laser irradiation was performed in air by picoseconds Nd: YAG laser. Defocused laser pulses had a laser spot on the sample surface of 3 mm in diameter and fluences of 0.057 and 0.11 J cm-2 . Laser beam was scanned over the 5x5 mm2 surface area with different steps along y-axes to provide a variation in deposited energy density. For structural and compositional characterisation following methods were used: Auger electron spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy and scanning electron microscopy. The obtained results show that laser processing at a lower fluence causes only oxidation of the top Ti layer, invariable to the number of applied laser pulses and no interlayer mixing was observed. Appliance of laser pulses at fluence of 0.11 J cm-2 , on the other hand, caused significant increase of surface roughness and partial and/or complete ablation of deposited layers, but in partially ablated regions considerable mixing between Ti and Ta films was registered. These experiments indicate that the use of picoseconds laser pulses w

During femtosecond interaction with surfaces, the processes of liquid and solid-state dewetting could be responsible for the generation and regrouping of nanoparticles and nanoparticle clusters. The occurrence of surface plasmon polariton most probably induces the LIPSS arrangement. We have used low-fluence scanning femtosecond beam to generate sub-wavelength periodic structures on multilayer Ni/Pd thin films on Si. The spatial period of LIPSS increases with the change of scanning directions in respect to the polarization direction due to the phase difference increase between the incoming and induced oscillations. (c) 2017 Elsevier B.V. All rights reserved.

The surface morphology of the ablation craters created in the multilayer 10x(Al/Ti)/Si system by nanosecond laser pulses at single- and dual wavelength has been studied experimentally and numerically. A complex multilayer thin film including ten (Al/Ti) bilayers deposited by ion sputtering on Si(1 0 0) substrate to a total thickness of 260 nm were illuminated at different laser irradiance in the range 0.25-3.5 x 10(9)W cm(-2). Single pulse laser irradiation was done at normal incidence in air, with the single wavelength, either at 532 nm or 1064 nm or with both laser light simultaneously in the ratio of 1: 10 for energy per pulse between second harmonic and 1064 nm. Most of the absorbed laser energy was rapidly transformed into heat, producing intensive modifications of composition and morphology on the sample surface. The results show an increase in surface roughness, formation of specific nanostructures, appearance of hydrodynamic features and ablation of surface material with crater formation. Applying a small fraction (10%) of the second harmonic in dual-wavelength pulses, a modification of the 10x(Al/Ti)/Si system by a single laser pulse was reflected in the formation of wider and/or deeper craters. Numerical calculations show that the main physical mechanism in ablation process is normal evaporation without phase explosion. The calculated and experimental results agree relatively well for the whole irradiance range, what makes the model applicable to complex Al/Ti multilayer systems. (C) 2015 Elsevier B.V. All rights reserved.

A study of the effects of laser irradiation on the morphology and composition of Ni/Ti multilayers induced by nanosecond laser pulses at different wavelengths is reported. Irradiation of complex 109(Ni/Ti)/Si sample was done by a Nd:YAG laser which operate at a 1064 nm wavelength, frequency doubled wavelength (532 nm) and dual-wavelength (1064 and 532 nm). The following surface morphological changes were observed: (1) ablation of the thin film during the first laser pulse and (2) appearance of some nanostructures (mosaic structure) in the irradiated region. After action of one pulse, the boundary of damage area was relatively sharp at low pulse energy, whereas it was diffuse after irradiation with higher energy per pulse. The results obtained show that laser irradiation induced mixing between Ni and Ti layers which creates conditions for the formation of intermetallic compounds. A numerical model was used to predict ablation depths and temperatures inside the material during the time. The model prediction shows a close agreement with experimental data.

The electrochemical exfoliation of graphite to give one-atom-thick graphene with desirable properties is a green, cost-effective method for high-yield graphene production. This paper presents the results of electrochemical exfoliation of two different graphite precursors under an applied direct current voltage of +12 V. The used characterization techniques (elemental analysis, Fourier transform infrared spectroscopy, X-ray diffraction, X-photoelectron spectroscopy, Raman spectroscopy, field emission scanning electron microscopy and atomic force microscopy) showed that the exfoliated powder is highly functionalized with a low carbon/oxygen content that is similar to graphene oxide. The exfoliated graphene sheets dispersed in N,N-dimethylformamide were deposited on ano-discs by vacuum filtration and transferred to glass ceramic substrates. The thermal annealing of the as-deposited films at 600 degrees C for 30 minutes resulted in an increase in the carbon/oxygen ratio by more than 3 fold and a decrease in the sheet resistance by 25%. The lowest values for the sheet resistance of the annealed graphene thin films were in the range of 0.32 +/- 0.04 to 0.84 +/- 0.1 kohm sq(-1) depending on the graphite source that was used.

Multilayer structures, consisting of 15 alternate Ti and Al thin films, and covered with thicker Ti layer, were deposited on a Si substrate to a total thickness of 900 nm. Laser treatment was performed in air by defocused Nd:YAG laser pulses (150 ps) with energies of 7 and 10 mJ covering an area of 3 mm in diameter (fluences were 0.1 and 0.14 J cm(-2) respectively). Laser beam was scanned over the 5 x 5 mm surface area. Characterizations were done by Auger electron spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscopy and transmission electron microscopy. Nano-hardness measurements were performed by Vickers method with applied load of 5 mN. Obtained results show that irradiation with picosecond laser pulses leads to the formation of Ti2O3 in the top Ti layer. This process is more pronounced for higher energy and/or higher number of applied laser pulses. On the surface of all samples very thin amorphous TiO2 layer was formed. Laser irradiation induces surface melting and transformation of relatively flat surface into mosaic shaped one for samples treated with higher energy and higher number of applied laser pulses. Irradiation at smaller energy did not induce any noticeably mixing between Al and Ti beneath the covered Ti layer. Some mixing of Al and Ti appeared in the sample irradiated with higher energy of laser pulses. (C) 2015 Elsevier B.V. All rights reserved.

The effects of helium ion irradiation on immiscible AlN/TiN multilayered system were studied. The structure consisted of 30 alternate AlN (similar to 8 nm) and TiN (similar to 9.3 nm) layers of a total thickness around 260 nm, deposited on (100) Si substrates by reactive sputtering. The system was then implanted with 30 keV He+ to very high irradiation doses, 1-4 x 10(17) ions/cm(2). Evaluated projected ion range was 153.1 +/- 45.4 nm and maximum displacements per atom for the applied doses from 6 to 24. It was found that the multilayers remained well separated and stable after irradiation to 1 x 10(17) ions/cm(2), which introduces up to 10 at.% of He within the structure. The main effects were agglomeration of He bubbles around the projected ion range, mostly concentrated at the AlN edges of the interfaces, and a slight increase of the mean grain size within the affected zone. Increasing of the ion dose induced further agglomeration of bubbles, splitting of the layers at the interfaces, and final destruction of the structure. The evaluated He content was consistent with the implanted dose up to 2 x 10(17) ions/cm(2). For the highest dose the implanted gas is partially released from the structure. The results can be interesting towards the development of radiation tolerant materials. (C) 2015 Elsevier B.V. All rights reserved.

In this paper, we performed synthesis of graphene thin films by rapid thermal annealing (RTA) of thin nickel copper (Ni/Cu) layers deposited on spectroscopic graphite as a carbon source. Furthermore, we investigated the effect of annealing temperature and annealing time on formation and quality of synthesized graphene films. Raman spectroscopy study showed that annealing at lower temperatures results in formation of monolayer graphene films, while annealing at higher temperatures results in formation of multilayer graphene films. We used Raman mapping to determine the distribution of graphene sheets. Surface morphology of graphene thin films was investigated by atomic force microscopy and scanning electron microscopy with EDS probe. (C) 2015 Elsevier B.V. All rights reserved.

Bimetallic NiAu and complex NiO:Au nanoparticles were formed by laser ablation of Ni target immersed in the colloidal gold solution. Effect of laser parameters (pulse duration, fluences and ablation times) on size and composition of nanoparticles was investigated by ablating the target with two Nd:YAG lasers at 1064 nm, operating with different pulse durations, 150 ps and 20 ns. Stronger ablation of the Ni target and subsequient synthesis of nanoparticles is achieved with picosecond pulses, compared to the nanoparticles production with nanosecond pulses, because the former ablation induces activation of different reactions between species in the colloidal solution. Shape, size and composition of the synthesized nanopraticles were found to correlate with the concentration of Ni species in the colloidal solution. Higher Ni concentration leads to formation of larger NiAu nanoparticles in form of solid solution. Smaller nanoparticles with lower Ni concentration in the colloidal solution were achieved by their synthesis during nanosecond pulses, when the obtained distribution of composition corresponds to the NiO matrix with incorporated golden nanoparticles. The results also demonstrate that the formation of bimetallic NiAu and complex NiO:Au nanoparticles were possible by means of laser ablation in liquids. (C) 2015 Elsevier B.V. All rights reserved.

In this paper we present synthesis of monolayer graphene islands. These films are deposited through nickel catalyzed transformation of fullerol and graphene quantum dots. Carbon doped nickel films are produced by autocatalytic chemical deposition. Upon rapid thermal annealing, graphene films are formed. Different characterization techniques are applied: Raman spectroscopy, scanning electron and atomic force microscopy. Raman spectroscopy analysis confirmed the formation of monolayer graphene films. Microscopy analysis revealed formation of monolayer islands.

The surface oxidation of Ni/Ti bilayer, deposited on silicon substrate, affected by picosecond Nd: YAG laser radiation has been investigated. Fluence close to the target ablation threshold and multi-pulse laser irradiation regime were applied. Changes in the chemical composition of the formed surface oxide layer were studied by Elastic Recoil Detection Analysis (ERDA) and X-ray photoelectron spectroscopy (XPS). Morphological features analysis, at the oxide surface layer, was monitored, too. Laser modification as-deposited (Ni/Ti)/Si sample with 10 pulses induces a progressed interaction between Ni and Ti layers with the initial surface oxidation and formation of NiTi alloy phase. Progressed intermixing of components was achieved for the irradiation with 50 and more pulses, when all components were quite uniformly distributed to a depth of about 80 nm. An oxide layer was formed at the surface, with the specific combination of the oxide phases depending on the number of accumulated pulses. Changes in the morphological characteristics are reflected in the increase of the mean surface roughness and the generation of a certain number of cavities. These features are decreased with increasing number of pulses, caused by the surface melting and a pronounced mobility of the materials. (C) 2013 Elsevier B.V. All rights reserved.

Enhanced conductivity, transparency and stability are the most important factors to consider in order to prepare electrodes for optoelectronic devices. In this paper, we investigated the properties of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films doped with graphene and graphene quantum dots. Samples were deposited by spin-coating onto glass substrates. Thin films were characterized by UV-vis and Raman spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM) and four-point probe measurements. It was found that both graphene and graphene quantum dots improve the conductivity of PEDOT:PSS films with only small decrease in transparency. AFM and SEM analysis showed homogenous distribution of spherical nanoparticles of graphene quantum dots and irregular shaped nanoparticles of graphene in PEDOT:PSS. (C) 2014 Elsevier B.V. All rights reserved.