The paper presents a method of producing single layers of molybdenum disulphide on silicon substrates covered with a layer of 275nm silicon dioxide produced by means of thermal oxidation. MoS2 was obtained using the CVD (Chemical Vapor Deposition) technique, and the process parameters were the heating temperatures of the substrates - sulfur and molybdenum oxide, the carrier gas flow in the reactor and the deposition time. Subsequently, the obtained layers were characterized using optical microscopy, atomic force microscopy and Raman spectroscopy. The obtained parameters of layers allow in the future to use them in sensory techniques.
Graphene due to its properties, such as high sensitivity and biocompatibility finds application in instruments that are used to cooperation with organic substances. At the same time, from the point of view of sensory devices, it is a material with high absorption potential that is able to improve sensitivity and selectivity of these devices. Another benefit of graphene application may be to use its properties in connection with ISFET – Ion Sensitive Field Effect Transistor, which operation principle is based mostly on detection of changes in hydrogen ions concentration. ISFET transistors ale produced in MOS technology, the difference between them and classic MOSFET (Metal-OxideSemiconductor Field Effect Transistor) structures is gate area, where gate metallization was replaced with reference electrode submerged in solution applied in this area. Properties of the solution determine transistor’s action. It is possible to make modifications in gate area of the structure which effects in changes of transistor’s properties. Example of such a modification may be application of graphene layer, which properties may significantly improve detecting capabilities of ISFET devices. For the needs of the research described in this work, graphene was deposited in gate area of transistors through transfer from cooper and germanium surfaces. To check correctness of ISFETs with graphene layer work, current – voltage characteristics of them were determined. Standard I-V characteristics with SiO2 as gate dielectric were compared with these where gate area was enriched with a graphene layer. Structures with graphene mostly worked properly. Thanks to the results presented in this work, it is possible to carry out further experiments using this structures and organic substances.
The AlN films were deposited using magnetron (Φ = 100 mm) and pulse power supplier (f = 100 kHz, with modulation of f = 2 kHz; current 3 A). Deposition processes were carried out at pressure of 2 Pa and using Ar/N2 gas mixture. The films were deposited on n-type silicon wafers located in parallel to aluminum target, keeping substrate-target distance at 15 cm. Round, titanium electrodes were evaporated on the top of deposited layers. Thus, metal-insulator-semiconductor (MIS) structures were created with aluminum nitride thin films playing the role of the insulator. Measurements of current-voltage (I-V) characteristics of MIS structures after annealing in different temperatures (300°C, 500°C), allowed to determine the leakage current density and critical electric field intensity (EBR) of investigated layers. Capacitance-voltage (C-V) measurements of the structures allowed to obtain the dielectric constant value (εri) of the films. Ellipsometric measurements allowed to obtain properties of deposited layer like thickness (29 nm), refraction index (1.855) and energy band gap (5.667 eV). Films’ microstructure was additionally studied using scanning electron microscope (SEM) and grazing X-ray diffraction (GXRD).
This work presents a technology of manufacturing silicon Metal Insulator Semiconductor/Ion Sensitive Field Effect Transistors (MIS/IS FETs) with DLC (Diamond-Like Carbon) as well as SiO2/DLC thin films in the role of gate dielectric. The crucial element of fabrication process was gate dielectric layer preparation. In the first case a thin DLC film was obtained by means of Radio Frequency Plasma Assisted Chemical Vapour Deposition (RF PECVD) directly onto the Si in the transistor gate area. In the second case whereas, prior to DLC deposition, a thin silicon dioxide buffer film was grown there using the high-temperature oxidation process. The photolithography allowed to open windows for formation of electric metal (Al) contacts to transistor source and drain regions. Contacts were obtained by means of vacuum evaporation. Subsequently, transfer and output current-voltage (I-V) characteristics of so produced transistors were measured and studied.
A luminescent lamp with field emission cathode was constructed and tested. Phosphor excited by electrons from field emission cathode is the source of light. The cathode is covered with nickel-carbon film containing multilayer carbon nanotubes that enhance electron emission from the cathode. Results of luminance stability measurements are presented. Luminance of elaborated luminance lamp is high enough for lighting application. Long term stability (1000 hours) is satisfactory for mass lamp application. Initial short time decrease of luminance is still too high and it needs reduction.
Carbon nanotube (CNT) films deposited on different porous silica substrates were studied by Scanning Electron Microscopy (SEM) and Raman Spectroscopy (RS). The films samples were prepared by a two-step method consisting of PVD and CVD processes. In the first step the nanocomposite Ni-C film was obtained by evaporation in dynamic vacuum from two separated sources of fullerenes and nickel acetate. Those films were deposited on porous silica and DLC/porous silica substrates. Analysis of SEM imaging showed that the obtained film are composed of carbon nanotubes, the distribution, size and quality of which depend on the type of substrate. The CNT films were studied by RS method to determine the influence of the substrate type on disordering of carbonaceous structure and quality of CNT in deposited films.
The aim of the study was to elucidate influence parameters of magnetron sputtering process on growth rate and quality of titanium dioxide thin films. TiO2 films were produced on two inch silicon wafers by means of magnetron sputtering method. Characterization of samples was performed using ellipsometer and atomic force microscope (AFM). Currentvoltage (I-V) and capacitance-voltage (C-V) measurements were also carried out. The results enable to determine impact of pressure, power, gases flow and process duration on the physical parameters obtained layers such as electrical permittivity, flat band voltage and surface topography. Experiments were designed according to orthogonal array Taguchi method. Respective trends impact were plotted.
Hafnium Oxide-Nitride films were deposited using reactive magnetron sputtering in O2/N2/Ar gas mixture. Deposition was planned according to Taguchi optimization method. Morphology of fabricated layers was tested using AFM technique (Ra=0.2÷1,0 nm). Thickness of HfOXNY films was measured using spectroscopic ellipsometry (t=45÷54 nm). Afterwards MIS structures were created by Al metallization process then layers were electrically characterised using I-V and C-V measurements. This allowed to calculate the electrical parameters of layers such as: flat-band voltage UFB, dielectric constant Ki, interface state trap density Dit and effective charge Qeff. Subsequently, deposited HfOxNy layers were annealed in PDA process (40 min 400 °C 100% N2) after which the electrical characterization was performed again.
The thin films of carbon-nickel (C-Ni) nanocoposites were deposited on Ti-evaporated Si (100) substrate using Physical Vapour Deposition (PVD) method. Influence of evaporated titanium on carbonaceous structure of C-Ni films were investigated by Raman spectroscopy method. The fullerite-graphite structure was recognize using principal component analysis (PCA) of obtained Raman spectra.
A series of test titanium electrodes, intended for a new generation of hydrogen and hydrogen compounds sensors was prepared. This new generation of hydrogen sensors is expected to operate in above normative conditions. In order to investigate the influence of temperature and moisture on titanium electrodes a series of experiments was conducted. Test samples were exposed to elevated levels of temperature (up to 165°C) and moisture (relative humidity up to 80%). These test allowed to measure resistivity as a function of temperature and to determine the long-term stability of electrical parameters of electrodes. Results of this studies will be used in fabrication of reliable electrodes for a new generation of hydrogen sensors.
C-Pd films were obtained by a two steps’ PVD/CVD method (Physical Vapor Deposition/Chemical Vapor Deposition). Investigations of Pd nanograins structure and carbon matrix structure were performed. Many types of substrates (Si, Si covered with DLC layer, Al2O3 plate and AAO membrane) with various developing specific surface area (SSA) were applied and the influence on this surface on obtained films C-Pd was studied. We present the results of Scanning Electron Microscopy (SEM) studies with SE (Secondary Electrons) and LABE (Low Angle Backscattered Electrons) modes. Depending on the substrate type it was possible to obtain many different films and structures with various structural features.
This work presents a study on sensing capabilities of stacks of nano-films deposited on a single-mode optical fiber end-faces. The stacks consist of periodically interchanging thin-film layers of materials characterized by different refractive indices (RI). The number of layers is relatively small to encourage light-analyte interactions. Two different deposition techniques are considered, i.e., radio frequency plasma enhanced chemical vapor deposition (RF PECVD) and physical vapor deposition by reactive magnetron sputtering (RMS). The former technique allows to deposit stacks consisting of silicon nitride nano-films, and the latter is well suited for aluminum and titanium oxides alternating layers. The structures are tested for external RI and temperature measurements.
In this work we compare effects of thin (<300 nm) aluminum oxide (Al2O3) deposition using advanced physical (Magnetron Sputtering - MS) and chemical (Atomic Layer Deposition – ALD) vapor deposition methods on optical fibers. We investigate an influence of the process parameters on optical properties of the nano-films deposited with MS. In order to investigate the properties of the films directly on the fibers, we induced long-period fiber grating (LPG) in the fiber prior the deposition. Thanks to LPG sensitivity to thickness and optical properties of the overlays deposited on the fiber, we are able to monitor Al2O3 nano-overlay properties. Moreover, we investigate an influence of the overlays deposited with both the methods on LPG-based refractive index (RI) sensing. We show and discuss tuning of the RI sensitivity by proper selection of both thickness and optical properties of the Al2O3 nano-overlays.
Reactive magnetron sputtering technique using O2/Ar gas mixture was used to deposit Gd2O3 layers. Following
metallization process of Al allowed to create MIS structures, which electrical parameters (κ, Dit, UFB, ρ, etc.) were
measured using high frequency C-V equipment. Created layers exhibit high permittivity (κ≈12) at 100kHz. I-V
measurements point out on maximum electric break down field Ebr≈0.4 MV/cm and maximum break down voltage Ubr ≈
16V. Layers were morphologically tested using AFM technique (Ra ≈ 0.5÷2nm). Layer thicknesses as well as refractive
indexes (RI ≈ 1.50÷2.05) were estimated using ellipsometry measurements.
Thin (100 nm) nanocrystalline dielectric films of lanthanum doped barium titanate were produced on Si substrates by
means of reactive impulse plasma ablation deposition (IPD) from BaTiO3 + La2O3 (2 wt.%) target. Scanning electron
microcopy and atomic force microscopy showed that the obtained layers were dense ceramics of uniform thickness with
average roughness Ra = 2.045 nm and the average grain size of the order of 15 nm. Measurements of current-voltage (IV)
characteristics of metal-insulator-semiconductor (MIS) structures, produced by evaporation of metal (Al) electrodes
on top of barium titanate films, allowed to determine that the leakage current density and critical electric field intensity
(EBR) of investigated layers ranged from 10-12 to 10-6 A cm-2 and from 0.2 to 0.5 MV cm-1, respectively. Capacitance-voltage
(C-V) measurements of the same structures were performed in accumulation state showing that the dielectric
constant value (εri) of films is of the order of 20.
In this paper we present studies of hydrogen sensors based on nanostructural C-Pd films deposited on alundum substrate
with silver or titanium electrodes. These C-Pd films were prepared by PVD method. Films were characterized by SEM
and EDS. Sensitivity of films toward hydrogen were measured in specially prepare experimental set-up with small
chamber (50ml). Response time was also registered for different percentage of hydrogen / nitrogen mixture (up to 1% of
hydrogen).
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