Surface Pattern over a Thick Silica Film to Realize Passive Radiative Cooling

Passive radiative cooling, which cools an item without any electrical input, has drawn much attention in recent years. In many radiative coolers, silica is widely used due to its high emissivity in the mid-infrared region. However, the performance of a bare silica film is poor due to the occurrence of an emitting dip (about 30% emissivity) in the atmospheric transparent window (8–13 μm). In this work, we demonstrate that the emissivity of silica film can be improved by sculpturing structures on its surface. According to our simulation, over 90% emissivity can be achieved at 8–13 μm when periodical silica deep grating is applied on a plane silica film. With the high emissivity at the atmospheric transparent window and the extremely low absorption in the solar spectrum, the structure has excellent cooling performance (about 100 W/m²). The enhancement is because of the coupling between the incident light with the surface modes. Compared with most present radiative coolers, the proposed cooler is much easier to be fabricated. However, 1-D gratings are sensitive to incident polarization, which leads to a degradation in cooling performance. To solve this problem, we further propose another radiative cooler based on a silica cylinder array. The new cooler’s insensitivity to polarization angle and its average emissivity in the atmospheric transparent window is about 98%. Near-unit emissivity and their simple structures enable the two coolers to be applied in real cooling systems.     

Synthesis and Characterisation of Nanocomposite Mo-Fe-B Thin Films Deposited by Magnetron Sputtering

Several ternary phases are known in the Mo-Fe-B system. Previous ab initio calculations have predicted that they should exhibit a tempting mix of mechanical and magnetic properties. In this study, we have deposited Mo-Fe-B films with a Fe-content varying from 0–37 at.% using non-reactive DC (direct current) magnetron sputtering. The phase composition, microstructure, and mechanical properties were investigated using X-ray diffraction, scanning transmission electron microscopy, and nanoindentation measurements. Films deposited at 300 °C and with >7 at.% Fe are nanocomposites consisting of two amorphous phases: a metal-rich phase and a metal-deficient phase. Hardness and elastic modulus were reduced with increasing Fe-content from ~29 to ~19 GPa and ~526 to ~353 GPa, respectively. These values result in H³/E² ratios of 0.089–0.052 GPa, thereby indicating brittle behaviour of the films. Also, no indication of crystalline ternary phases was observed at temperatures up to 600 °C, suggesting that higher temperatures are required for such films to form.     

Interfacial Chemical Effects of Amorphous Zinc Oxide/Graphene

Research on the preparation and performance of graphene composite materials has become a hotspot due to the excellent electrical and mechanical properties of graphene. Among such composite materials, zinc oxide/graphene (ZnO/graphene) composite films are an active research topic. Therefore, in this study, we used the vacuum thermal evaporation technique at different evaporation voltages to fabricate an amorphous ZnO/graphene composite film on a flexible polyethylene terephthalate (PET). The amorphous ZnO/graphene composite film inherited the great transparency of the graphene within the visible spectrum. Moreover, its electrical properties were better than those of pure ZnO but less than those of graphene, which is not consistent with the original theoretical research (wherein the performance of the composite films was better than that of ZnO film and slightly lower than that of graphene). For example, the bulk free charge carrier concentrations of the composite films (0.13, 1.36, and 0.47 × 10¹⁸ cm⁻³ corresponding to composite films with thicknesses of 40, 75, and 160 nm) were remarkably lower than that of the bare graphene (964 × 10¹⁸ cm⁻³) and better than that of the ZnO (0.10 × 10¹⁸ cm⁻³). The underlying mechanism for the abnormal electrical performance was further demonstrated by X-ray photoelectron spectroscopy (XPS) detection and first-principles calculations. The analysis found that chemical bonds were formed between the oxide (O) of amorphous ZnO and the carbon (C) of graphene and that the transfer of the π electrons was restricted by C=O and C-O-C bonds. Given the above, this study further clarifies the mechanism affecting the photoelectric properties of amorphous composite films.     

In Situ Monitoring of Pulsed Laser Annealing of Eu-Doped Oxide Thin Films

Eu³⁺-doped oxide thin films possess a great potential for several emerging applications in optics, optoelectronics, and sensors. The applications demand maximizing Eu³⁺ photoluminescence response. Eu-doped ZnO, TiO_2, and Lu₂O₃ thin films were deposited by Pulsed Laser Deposition (PLD). Pulsed UV Laser Annealing (PLA) was utilized to modify the properties of the films. In situ monitoring of the evolution of optical properties (photoluminescence and transmittance) at PLA was realized to optimize efficiently PLA conditions. The changes in optical properties were related to structural, microstructural, and surface properties characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). The substantial increase of Eu³⁺ emission was observed for all annealed materials. PLA induces crystallization of TiO₂ and Lu₂O₃ amorphous matrix, while in the case of already nanocrystalline ZnO, rather surface smoothening0related grains’ coalescence was observed.     

Structural Properties of Thin ZnO Films Deposited by ALD under O-Rich and Zn-Rich Growth Conditions and Their Relationship with Electrical Parameters

The structural, optical, and electrical properties of ZnO are intimately intertwined. In the present work, the structural and transport properties of 100 nm thick polycrystalline ZnO films obtained by atomic layer deposition (ALD) at a growth temperature (T_g) of 100–300 °C were investigated. The electrical properties of the films showed a dependence on the substrate (a-Al₂O₃ or Si (100)) and a high sensitivity to T_g, related to the deviation of the film stoichiometry as demonstrated by the RT-Hall effect. The average crystallite size increased from 20–30 nm for as grown samples to 80–100 nm after rapid thermal annealing, which affects carrier scattering. The ZnO layers deposited on silicon showed lower strain and dislocation density than on sapphire at the same T_g. The calculated half crystallite size (D/2) was higher than the Debye length (L_D) for all as grown and annealed ZnO films, except for annealed ZnO/Si films grown within the ALD window (100–200 °C), indicating different homogeneity of charge carrier distribution for annealed ZnO/Si and ZnO/a-Al₂O₃ layers. For as grown films the hydrogen impurity concentration detected via secondary ion mass spectrometry (SIMS) was 10²¹ cm⁻³ and was decreased by two orders of magnitude after annealing, accompanied by a decrease in Urbach energy in the ZnO/a-Al₂O₃ layers.     

Analytical Study of Porous Organosilicate Glass Films Prepared from Mixtures of 1,3,5- and 1,3-Alkoxysilylbenzenes

Organosilicate glass (OSG)-based porous low dielectric constant (low-k) films with different molar ratios of 1,3,5-tris(triethoxysilyl)benzene to 1,3-bis(triethoxysilyl)benzene bridging organic groups (1:3 and 1:7) were spin-on deposited, followed by a soft bake in air and N₂ at 150 °C and hard bake in air and N₂ at 400 °C. Non-ionic template (Brij^®30) concentrations were varied from 0 to 41 wt% to control the porosity of the films. The chemical composition of the matrix of the films was evaluated and discussed with the shrinkage of the film during the curing, refractive indices, mechanical properties, k-values, porosity and pore structure. The chemical composition of the film cured in both air and N₂-containing ambient were evaluated and compared. The benzene bridging groups containing films change their porosity (0 to 43%) but keep the pore size constant and equal to 0.81 nm when porosity is lower than 30%. The k-value decreases with increasing porosity, as expected. The films containing benzene bridge have higher a Young’s modulus than plasma-enhanced chemical vapor deposition (PECVD) methyl-terminated low-k films with the same porosity and show good hydrophobic properties after a hard bake and close to the values reported for 1,4-benzene-bridged films. The fabricated films show good stability after a long time of storage. However, the improvement of mechanical properties was lower than the values predicted by the published literature data. It was concluded that the concentration of 1,3,5-benzene bridges was below the stiffness threshold required for significant improvement of the mechanical properties. The films show UV-induced luminescence with a photon energy of 3.6 to 4.3 eV. The luminescence is related to the presence of oxygen-deficient-type defects or their combination with organic residues. The most intensive luminescence is observed in as-deposited and soft bake samples, then the intensity is reduced after a hard bake. It is assumed that the oxygen-deficient centers form because of the presence of Si–OC₂H₅ groups in the films and the concentration of these centers reduces when all these groups completely transformed into siloxane (Si–O–Si).     

Effect of the Source-to-Substrate Distance on Structural,Optoelectronic, and Thermoelectric Properties of Zinc Sulfide Thin Films

Zinc sulfide (ZnS) thin films with variable structural, optical, electrical, and thermoelectric properties were obtained by changing the source-to-substrate (SSD) distance in the physical-vapor-thermal-coating (PVTC) system. The films crystallized into a zinc-blende cubic structure with (111) preferred orientation. The films had a wide 3.54 eV optical band gap. High-quality homogenous thin films were obtained at 60 mm SSD. The sheet resistance and resistivity of the films decreased from 10¹¹ to 10¹⁰ Ω/Sq. and from 10⁶ to 10⁵ Ω-cm, when SSD was increased from 20 mm to 60 mm, respectively. The phase and band gap were also verified by first principles that were in agreement with the experimental results. Thermoelectric characteristics were studied by using the semi-classical Boltzmann transport theory. The high quality, wide band gap, and reduced electrical resistance make ZnS a suitable candidate for the window layer in solar cells.     

The Effects of Zr Doping on the Optical,Electrical and Microstructural Properties of Thin ZnO Films Deposited by Atomic Layer Deposition

Transparent conducting oxides (TCOs), with high optical transparency (≥85%) and low electrical resistivity (10⁻⁴ Ω·cm) are used in a wide variety of commercial devices. There is growing interest in replacing conventional TCOs such as indium tin oxide with lower cost, earth abundant materials. In the current study, we dope Zr into thin ZnO films grown by atomic layer deposition (ALD) to target properties of an efficient TCO. The effects of doping (0–10 at.% Zr) were investigated for ~100 nm thick films and the effect of thickness on the properties was investigated for 50–250 nm thick films. The addition of Zr⁴⁺ ions acting as electron donors showed reduced resistivity (1.44 × 10⁻³ Ω·cm), increased carrier density (3.81 × 10²⁰ cm⁻³), and increased optical gap (3.5 eV) with 4.8 at.% doping. The increase of film thickness to 250 nm reduced the electron carrier/photon scattering leading to a further reduction of resistivity to 7.5 × 10⁻⁴ Ω·cm and an average optical transparency in the visible/near infrared (IR) range up to 91%. The improved n-type properties of ZnO: Zr films are promising for TCO applications after reaching the targets for high carrier density (>10²⁰ cm⁻³), low resistivity in the order of 10⁻⁴ Ω·cm and high optical transparency (≥85%).     

Origin of Mangetotransport Properties in APCVD Deposited Tin Oxide Thin Films

Transparent conducting oxides (TCO) with high electrical conductivity and at the same time high transparency in the visible spectrum are an important class of materials widely used in many devices requiring a transparent contact such as light-emitting diodes, solar cells and display screens. Since the improvement of electrical conductivity usually leads to degradation of optical transparency, a fine-tuning sample preparation process and a better understanding of the correlation between structural and transport properties is necessary for optimizing the properties of TCO for use in such devices. Here we report a structural and magnetotransport study of tin oxide (SnO₂), a well-known and commonly used TCO, prepared by a simple and relatively cheap Atmospheric Pressure Chemical Vapour Deposition (APCVD) method in the form of thin films deposited on soda-lime glass substrates. The thin films were deposited at two different temperatures (which were previously found to be close to optimum for our setup), 590 °C and 610 °C, and with (doped) or without (undoped) the addition of fluorine dopants. Scanning Electron Microscopy (SEM) and Grazing Incidence X-ray Diffraction (GIXRD) revealed the presence of inhomogeneity in the samples, on a bigger scale in form of grains (80–200 nm), and on a smaller scale in form of crystallites (10–25 nm). Charge carrier density and mobility extracted from DC resistivity and Hall effect measurements were in the ranges 1–3 × 10²⁰ cm⁻³ and 10–20 cm²/Vs, which are typical values for SnO₂ films, and show a negligible temperature dependence from room temperature down to −269 °C. Such behaviour is ascribed to grain boundary scattering, with the interior of the grains degenerately doped (i.e., the Fermi level is situated well above the conduction band minimum) and with negligible electrostatic barriers at the grain boundaries (due to high dopant concentration). The observed difference for factor 2 in mobility among the thin-film SnO₂ samples most likely arises due to the difference in the preferred orientation of crystallites (texture coefficient).     

Development of Shrimp Freshness Indicating Films by Embedding Anthocyanins-Rich Rhododendron simsii Flower Extract in Locust Bean Gum/Polyvinyl Alcohol Matrix

Freshness indicating films containing anthocyanins are one type of smart packaging technology. Anthocyanins in the films can show visual color changes when food spoilage occurs, thereby indicating the freshness degree of food in real-time. Rhododendron simsii is a landscape plant with attractive flowers that are abundant in anthocyanins. In this study, smart packaging films were prepared by embedding 2% and 4% R. simsii flower anthocyanins (RA) in locust bean gum- (LBG) and polyvinyl alcohol- (PVA) based matrices. The micro-structure, barrier, mechanical, thermal, antioxidant, and color-changeable properties of the films were determined. The potential application of the films in indicating the freshness of shrimp at 4 °C was also investigated. Results showed that the RA interacted with the LBG/PVA matrices through hydrogen bonds, which significantly improved the barrier, mechanical, thermal, antioxidant, pH-sensitive, and ammonia-sensitive properties of the films. Meanwhile, the performance of the films was remarkably influenced by the content of the RA. The film containing 4% RA had the highest light blocking ability, tensile strength (38.32 MPa), elongation at break (58.18%), and antioxidant activity, and also showed the lowest water vapor permeability (22.10 × 10⁻¹¹ g m⁻¹ s⁻¹ Pa⁻¹) and oxygen permeability (0.36 cm³ mm m⁻² day⁻¹ atm⁻¹). The films containing 2% and 4% RA could effectively change their colors when the level of total volatile basic nitrogen in the shrimp exceeded the safe value, which demonstrated the suitability of the films for indicating the freshness degree of shrimp.     

Influence of Different Solvents and High-Electric-Field Cycling on Morphology and Ferroelectric Behavior of Poly(Vinylidene Fluoride-Hexafluoropropylene) Films

P(VdF-HFP) films are fabricated via a solution casting doctor blade method using high (HVS) and low (LVS) volatile solvents, respectively. The structural properties and the ferroelectric behavior are investigated. The surface structure and crystal phase composition are found to be strongly dependent on the type of solvent. LVS leads to a rougher copolymer surface structure with large spherulites and a lower crystallinity in contrast with HVS. The crystalline phase of copolymer films fabricated with HVS consists almost exclusively of α-phase domains, whereas films from LVS solution show a large proportion of γ-phase domains, as concluded from Raman and X-ray diffraction spectra. Virgin films show no ferroelectric (FE) switching polarization at electric field amplitudes below 180 MV/m, independent of the solvent type, observed in bipolar dielectric displacement—electric field measurements. After applying electric fields of above 180 MV/m, a FE behavior emerges, which is significantly stronger for LVS films. In a repeated measurement, FE polarization switching already occurs at lower fields. A shielding effect may be related to this observation. Additionally, Raman bands of polar γ-phase increase by high-electric-field cycling for the LVS sample. The solvent used and the resulting crystal phase composition of the virgin sample is crucial for the copolymer behavior during bipolar electrical cycling.     

Molybdenum Oxide Thin Films Grown on Flexible ITO-Coated PET Substrates

Molybdenum oxide thin films were deposited on stiff and flexible substrates by reactive DC magnetron sputtering. Two sets of samples were prepared. The first with different O₂/Ar flow rate ratios and the second, fixing the oxygen content, with different time of deposition. As the O₂/Ar flow rate ratio varies from 0 up to 0.56, a threshold was found, ranging from crystalline to amorphous nature, and from a nontransparent appearance with metallic-like electrical conductivity to transparent and dielectric behaviour. From the second set, all transparent, the MoO_x films present a compact/dense and featureless morphology with thickness from 190 up to 910 nm, depending on the time of deposition. Their structure was corroborated by XPS and Rutherford Backscattering Spectrometry (RBS) and density measurements were performed by RBS and X-ray reflectivity (XRR), revealing a value of 2.4 g/cm³. The surface roughness is in the order of a few nanometers and the maxima optical transmission, in the visible range, is around 89%. Electrochemical cyclic voltammograms showed noticeable color reversibility and reproducibility on the flexible substrates opening new framework possibilities for new electrochomic devices.     

Voltammetric Studies on Gold Electrodes Coated with Chitosan-Containing Layer-by-Layer Films

Gold (Au) electrodes coated with layer-by-layer (LbL) thin films composed of chitosan (CHI) were prepared to evaluate the redox properties of hexaammine ruthenium ions, Ru(NH₃)₆³⁺, and ferricyanide ions, Fe(CN)₆³⁻ LbL films were prepared on an Au electrode by electrostatic LbL deposition using polycationic CHI and poly(vinyl sulfate) (PVS) or poly(acrylic acid) (PAA) as anionic component. Redox peak current in cyclic voltammetry of Ru(NH₃)₆³⁺ on the CHI/PVS and CHI/PAA film-coated electrodes increased with increasing thickness of the films. Interestingly, the cyclic voltammograms showed two pair of redox peaks, originating from Ru(NH₃)₆³⁺ diffusing across the LbL layers and from those confined in the film. The results were rationalized in terms of the electrostatic interactions between Ru(NH₃)₆³⁺ and excess negative charges in the LbL films originating from PVS and PAA. In contrast, Fe(CN)₆³⁻ was not confined in the LbL films due to electrostatic repulsion of Fe(CN)₆³⁻ and excess negative charges. Significant amounts of Ru(NH₃)₆³⁺ were confined in the films at pH 7.0, whereas few ions were bound at pH 3.0 due to the reduced net negative charge in the films. The results suggest a potential use of the CHI-containing LbL films as scaffold for immobilizing positively charged ionic species on the electrode surface.     

Development of Eco-Sustainable PBAT-Based Blown Films and Performance Analysis for Food Packaging Applications

In this work, eco-sustainable blown films with improved performance, suitable for flexible packaging applications requiring high ductility, were developed and characterized. Films were made by blending two bioplastics with complementary properties—the ductile and flexible poly(butylene-adipate-co-terephthalate) (PBAT) and the rigid and brittle poly(lactic acid) (PLA)—at a 60/40 mass ratio. With the aim of improving the blends’ performance, the effects of two types of PLA, differing for viscosity and stereoregularity, and the addition of a commercial polymer chain extender (Joncryl^®), were analyzed. The use of the PLA with a viscosity ratio closer to PBAT and lower stereoregularity led to a finer morphology and better interfacial adhesion between the phases, and the addition of the chain extender further reduced the size of the dispersed phase domains, with beneficial effects on the mechanical response of the produced films. The best system composition, made by the blend of PBAT, amorphous PLA, and the compatibilizer, proved to have improved mechanical properties, with a good balance between stiffness and ductility and also good transparency and sealability, which are desirable features for flexible packaging applications.     

Investigation of High-Temperature Normal Infrared Spectral Emissivity of ZrO2 Thermal Barrier Coating Artefacts by the Modified Integrated Blackbody Method

Zirconium oxide (ZrO₂) is widely used as the thermal barrier coating in turbines and engines. Accurate emissivity measurement of ZrO₂ coating at high temperatures, especially above 1000 °C, plays a vital role in thermal modelling and radiation thermometry. However, it is an extremely challenging enterprise, and very few high temperature emissivity results with rigorously estimated uncertainties have been published to date. The key issue for accurately measuring the high temperature emissivity is maintaining a hot surface without reflection from the hot environment, and avoiding passive or active oxidation of material, which will modify the emissivity. In this paper, a novel modified integrated blackbody method is reported to measure the high temperature normal spectral emissivity of ZrO₂ coating in the temperature range 1000 °C to 1200 °C and spectral range 8 μm to 14 μm. The results and the associated uncertainty of the measurement were estimated and a relative standard uncertainty better than 7% (k = 2) is achieved.     

Polydopamine-Supported Lipid Bilayers

We report the formation of lipid membranes supported by a soft polymeric cushion of polydopamine. First, 20 nm thick polydopamine films were formed on mica substrates. Atomic force microscopy imaging indicated that these films were also soft with a surface roughness of 2 nm under hydrated conditions. A zwitterionic phospholipid bilayer was then deposited on the polydopamine cushion by fusion of dimyristoylphosphatidylcholine (DMPC) and dioleoylphosphatidylcholine (DOPC) vesicles. Polydopamine films preserved the lateral mobility of the phospholipids as shown by fluorescence microscopy recovery after photobleaching (FRAP) experiments. Diffusion coefficients of ~5.9 and 7.2 µm² s⁻¹ were respectively determined for DMPC and DOPC at room temperature, values which are characteristic of lipids in a free standing bilayer system.     

Study of Growth and Properties of Electrodeposited Sodium Iron Hexacyanoferrate Films

Sodium iron hexacyanoferrate (NaFeHCF) films were electrodeposited on Au/Cr/Si for the study of growth behavior and physical properties. The NaFeHCF films were studied by different analytical methods to prove the chemical composition, morphology and crystal structure. The grains of the film grow with a cubic structure with an average lattice parameter of 10.10 Å and the preferential growth direction along the [111] direction of the cubic cell. The films show a repeatable bipolar resistive switching behavior accompanied by high current changes (up to a factor of ~10⁵). The different resistive states in the materials are dominated by ohmic conduction.     

Orodispersible Films with Rupatadine Fumarate Enclosed in Ethylcellulose Microparticles as Drug Delivery Platform with Taste-Masking Effect

Orally disintegrating (orodispersible) films provide a versatile tool for drug administration, especially in the pediatric and geriatric population, since they reduce the risk of choking and do not necessitate drinking water during application. By considering their direct contact with the taste buds, palatability is an influential aspect related to patient compliance. The microparticles based on taste-masking polymers containing drugs enclosed inside effectively mask the unpleasant taste of medicines. Ethylcellulose is a hydrophobic polymer widely used as a taste-masking material. Rupatadine fumarate, a second-generation antihistamine drug, is characterised by an intense bitter taste; therefore, it is crucial to achieve a tolerable taste whilst developing orodispersible formulations with its content. The objective of this study was to develop orally disintegrating films with rupatadine fumarate in the form of ethylcellulose-based microparticles obtained from aqueous dispersions of ethylcellulose—Surelease^® or Aquacoat^® ECD. It was a technological challenge to achieve homogenous drug content per dosage unit and sufficient mechanical properties for film operating due to the necessity to suspend the microparticles in the casting solution. Although the process of obtaining films consisted of several steps (mixing, pouring, drying), the particles were homogeneously dispersed, and each film of the desired size contained the proper dose of the drug. The taste-masking effect was also maintained. This parameter was confirmed by three independent methods: in vivo by healthy volunteers, an electronic tongue and a dissolution test. The applied taste-evaluation techniques showed that the films containing Aquacoat^® ECD microparticles have the highest degree of bitter taste reduction, which confirms the results obtained in our previous studies.     

Polar Phonon Behaviour in Polycrystalline Bi-Doped Strontium Titanate Thin Films

Strontium titanate-based materials with ferroelectric or relaxor-like properties have drawn vast attention as polar dielectrics for electronics and telecommunications. Here, we study the lattice dynamics in sol–gel-derived Sr_1−1.5xBi_xTiO₃ thin films with x = 0.0053 and 0.167, deposited on Al₂O₃ substrates, using a variable-temperature far-infrared spectroscopy in a transmittance mode. Bi doping, known to induce a low-frequency dielectric relaxation in SrTiO₃ (ST) ceramics and films, due to off-centre dopant ion displacements generating electric dipoles, is shown to affect the polar phonon behaviour of thin films. We show that in weakly Bi-doped films, the low-frequency polar TO1 mode softens on cooling but less than in undoped ST. In heavily Bi-doped ST films, this mode displays no significant frequency variation with temperature from 300 to 10 K. The polar phonon behaviour of polycrystalline Bi-doped ST thin films is comparable with that of Bi-doped ST ceramics, which exhibit dielectric relaxations and harden soft-mode behaviour instead of the ferroelectric phase transition.     

The Role of Ambient Gas and Pressure on the Structuring of Hard Diamond-Like Carbon Films Synthesized by Pulsed Laser Deposition

Hard carbon thin films were synthesized on Si (100) and quartz substrates by the Pulsed Laser Deposition (PLD) technique in vacuum or methane ambient to study their suitability for applications requiring high mechanical resistance. The deposited films’ surface morphology was investigated by scanning electron microscopy, crystalline status by X-ray diffraction, packing and density by X-ray reflectivity, chemical bonding by Raman and X-ray photoelectron spectroscopy, adherence by “pull-out” measurements and mechanical properties by nanoindentation tests. Films synthesized in vacuum were a-C DLC type, while films synthesized in methane were categorized as a-C:H. The majority of PLD films consisted of two layers: one low density layer towards the surface and a higher density layer in contact with the substrate. The deposition gas pressure played a crucial role on films thickness, component layers thickness ratio, structure and mechanical properties. The films were smooth, amorphous and composed of a mixture of sp³-sp² carbon, with sp³ content ranging between 50% and 90%. The thickness and density of the two constituent layers of a film directly determined its mechanical properties.