Интерференционная фотолитография с использованием эффекта фототравления в халькогенидных пленках

The surface roughness of thin amorphous films of chalcogenide glasses (ChG) after photostimulated dissolution in amine-based selective etchant has been investigated. It is established that the rms roughness of the annealed and photoetched ChG film substantially smaller than the as-evaporated film and etched in the same selective etchant. This makes it possible to obtain more higher-quality lithographic masks or periodic relief-phase structures using new photoetching effect: photo-induced enhancement in solubility of annealed ChG layers. A possible mechanism for the photoinduced etching of ChGs is discussed. The diffraction gratings on germanium ChG - more environmentally acceptable compounds than traditionally used arsenic chalcogenides, were recorded for the first time by using the effect of hotoinduced etching on ChG layers and their characteristics were studiedДосліджено шорсткість поверхні тонких плівок аморфних халькогенідних стекол (CHG) після фотостимульованого розчинення в селективних травниках на основі амінів. Встановлено, що середньоквадратична шорсткість поверхні відпаленої та фототравленої ChG-плівки значно менша, ніж осадженої і травленої в тому ж селективному травнику плівки. Використання нового ефекту фототравлення – фотоіндукованого підвищення розчинності відпалених ChG шарів – дає можливість отримати літографічні маски або періодичні рельєфно-фазові структури вищої якості. Обговорюється можливий механізм фотоіндукованого травлення CHG-плівок. Вперше записані з використанням ефекту фотоіндукованого травлення дифракційні гратки на германієвих CHG, екологічно прийнятніші сполук, ніж традиційно використовуваних халькогенідів миш'яку; вивчено їх характеристики.Исследована шероховатость поверхности тонких пленок аморфных халькогенидных стекол (CHG) после фотостимулированного растворения в селективных травителях на основе аминов. Установлено, что среднеквадратичная шероховатость поверхности отожженной и фототравленой ChG-пленки значительно меньше, чем осажденной и травленной в том же селективном травителе пленки. Использование нового эффекта фототравления - фотоиндуцированного повышения растворимости отожженных ChG слоев - дает возможность получить литографические маски или периодические рельефно-фазовые структуры высшего качества. Обсуждается возможный механизм фотоиндуцированного травления CHG-пленок. Впервые записаны с использованием эффекта фотоиндуцированного травления дифракционные решетки на германиевых CHG, экологически более приемлемом соединении, чем традиционно используемых халькогенидов мышьяка; изучены их характеристики

Nickel-induced enhancement of photoluminescence in nc-Si–SiOx nanostructures

The effect of nickel silicide interlayer on the intensity of photoluminescence (PL) from Si nanoclusters (nc) in normally deposited and obliquely deposited in vacuum SiOx/Ni/Si structures have been studied using spectral and time-resolved PL measurements. It has been shown that the intensity of PL band in SiOx/Ni/Si samples is essentially higher than that in reference SiOx/Si samples (without the nickel interlayer) with the same characteristics and treatment. The PL intensity enhancement factor is equal to 5.77 for normally deposited samples and 18 for obliquely deposited samples. The unchanged spectral shape of PL bands and similar position of PL maximum in samples with and without nickel silicide interlayer indicates that in the SiOx/Ni/Si structures after annealing no additional emitting centers are introduced to compare with reference one. Time-resolved measurements showed that PL decay rate was decreased from 8.2*10⁴ s⁻¹ for SiOx/Si specimens to 2.86*10⁴ s⁻¹ for SiOx/Ni/Si one. The emission decay rate distribution was determined by fitting the experimental decay curves to the stretchedexponential model. The observed narrow decay rate distribution, decrease of the PL decay rate and enhancement of the PL intensity in SiOx/Ni/Si samples can be assigned to the processes of nickel silicide passivation of the dangling bonds at the interface of Si nanoparticles and the silicon oxide matrix, which is more effective in porous samples

Photostimulated etching of germanium chalcogenide films

The new effect of photostimulated dissolution of as-evaporated and annealed Ge-based chalcogenide glass (ChG) films was investigated in detail. The etching rate increases with the illumination intensity, and its spectral dependence is correlated with absorption in the film at the absorption edge. A possible mechanism for the photoinduced etching of ChG films has been discussed. The high-frequency diffraction gratings on germanium ChG – more environmentally acceptable compounds than traditionally used arsenic chalcogenides – were recorded using the method of interference immersion photolithography with photoinduced etching

Controlling the photoluminescence spectra of porous nc-Si–SiOx structures by vapor treatment

The effect of HF and H₂O₂ vapor treatment on the spectral composition and intensity of photoluminescence (PL) in porous oblique deposited nc-Si–SiOx structures have been studied using FTIR, electron-spin resonance (EPR) and PL measurements. As a result of HF vapor treatment, considerable PL intensity growth and blueshift of PL peak position are observed. It is suggested that the evolution of the PL spectra in HF vapor-treated samples can be attributed to selective-etching-induced decrease in Si nanoparticle dimensions and to passivation of Si dangling bonds (that are nonradiative recombination trap states) by hydrogen and oxygen. Additional treatment in H₂O₂ vapor results in additional nc-Si surface oxidation and reduction of nc-Si size. The possibility to control the PL characteristics (peak position and intensity) of the porous nc-Si–SiOx structures in a wide range by above treatments is shown

Nanopatterning Au chips for SPR refractometer by using interference lithography and chalcogenide photoresist

This study reports on development of the interference lithography (IL) technique applying the resist based on chalcogenide glass films for fabrication of gold chips in the nform of periodic surface nanostructures for surface plasmon resonance (SPR) refractometers. The IL technique was optimized for patterning the Au layers and formation of one-dimensional (grating) structures with the spatial frequency close to 3300 mm⁻¹. The spatial frequency and depth of grating grooves were selected with account of the condition for Bragg reflection of plasmons at the operation wavelength of SPR refractometer and given environment (which is a condition for enhancing biosensor sensitivity as compared to that of a flat Au chip surface). It has experimentally been demonstrated that the use of diffraction patterns in SPR sensor increases its response by 17%

Смуга фіолетової люмінесценції в тонких плівках ZnO і ZnO-Ag

The stationary and time-resolved photoluminescence (PL) spectra of ZnO films deposited on different substrates were studied. The intensive violet (V) emission centred at about 415–420 nm was observed at room temperature in photoluminescence (PL) spectra of the ZnO films. We found that the V-band is observed in all types of film, regardless of the type of substrate or the presence of a dopant. The ratio of intensities of violet and ultraviolet (UV) bands depends on temperature and duration of the heat treatment. It is also shown that the V band is not associated exclusively with the film surface states; instead, it is inherent in both the surface and the entire volume. The V band is of a complex shape and consists of 3 sub-bands with the maxima at 408, 414, and 421 nm. The relative contribution of each of the sub-bands is determined by the technological conditions of the film preparation. Analysis of obtained data allows us to conclude that the V-band is due to intrinsic defects of the ZnO film and can be attributed to the near band edge emission of ZnO

Preparation, structural and luminescent properties of nanocrystalline ZnO films doped Ag by close space sublimation method

The simple way for silver doping of ZnO films is presented. The ZnO films were prepared by reactive rf-magnetron sputtering on silicon and sapphire substrates. Ag doping is carried out by sublimation of the Ag source located at close space at atmospheric pressure in air. Then the ZnO and ZnO–Ag films were annealed in wet media. The microstructure and optical properties of the films were compared and studied by atomic force microscopy (AFM), X-ray diffraction (XRD), photoluminescence (PL) and cathodoluminescence (CL). XRD results indicated that all the ZnO films have a polycrystalline hexagonal structure and a preferred orientation with the c-axis perpendicular to the substrate. The annealing and Ag doping promote increasing grain’s sizes and modification of grain size distribution. The effect of substrate temperature, substrate type, Ag doping and post-growth annealing of the films was studied by PL spectroscopy. The effect of Ag doping was obvious and identical for all the films, namely the wide visible bands of PL spectra are suppressed by Ag doping. The intensity of ultraviolet band increased 15 times as compared to their reference films on sapphire substrate. The ultraviolet/visible emission ratio was 20. The full width at half maximum (FWHM) for a 380 nm band was 14 nm, which is comparable with that of epitaxial ZnO. The data implies the high quality of ZnO–Ag films. Possible mechanisms to enhance UV emission are discussed

Preparation, structural and luminescent properties of nanocrystalline ZnO film doped Ag by close space sublimation method

A simple way for silver doping of ZnO films presented. The effect of substrate temperature, substrate type, Ag doping and post-growth annealing of the film was studies by PL spectroscopy, XRD, AFM methods