Zbigniew Lukasiak

Optical properties of metallophthalocyanine compounds thin films

This work contains investigation results of the linear and nonlinear optical properties of metallophthalocyanines (Cu, Co, Zn, and Mg) and metallophthalocyanine chlorides (Al, Ga) thin films which were grown by physical vapor deposition (PVD) technique in high vacuum on transparent (quartz) and semiconductor (silica) substrates. Spectral properties of these films were examined using transmission, SGH and THG technique. Structural properties were investigated by AFM measurements. Transmission spectra were shown a large influence of intermolecular interaction on spectral properties of metallophthalocyanines and metallophthalocyanine chlorides. The influence of films thickness and annealing process of samples on their optical properties were also determined. The thickness dependence was connected with morphology of the film while annealing was caused change in polymorph phase. The measurements of transmission, SHG and THG spectra were allowed to determine optical constant of these films.

Photoluminescence of electrochemically etched porous silicon coated with small-molecule based thin organic films

In this paper, photoluminescence (PL) spectra of porous silicon (PSi) prepared by electrochemical anodisation coated with small-molecule based thin organic films are presented. Thin layers of copper phthalocyanine (CuPc) and tris(8-hydroxyquinoline) aluminium (Alq3) were deposited on PSi using the conventional thermal evaporation in high vacuum. Presented structures exhibit strong photoluminescence in visible region at room temperature under pulsed UV excitation. PL spectra of Alq3 deposited on glass and PSi layer without organic film are presented for intercomparison. The shapes of PL spectra of PSi/organic structures depends on material used and exhibit multiband structure. Properties of PSi/organic luminescence can be explained by penetration of organic material into PSi skeleton and interaction between carriers in PSi and deposited material.

Grown of ZnO:Ce layers by spray pyrolysis method for nonlinear optical studies

We have investigated the linear and nonlinear optical properties of high quality cerium-doped zinc oxide films (ZnO:Ce). The layers were grown by the reactive chemical pulverization spray pyrolysis technique using zinc and cerium chlorides as precursors at temperature up to 450/spl deg/C. The influence of Ce concentration on the structural, linear and nonlinear optical properties of ZnO thin films is presented. The films were characterized by X-ray diffraction, scanning electron microscope and photoluminescence measurements. The X-ray diffraction analysis indicates that all films are polycrystalline in nature and clearly shows the appropriate incorporation of the Ce atoms in the ZnO films. The third order nonlinear optical properties, which are the main subject of this investigation, were studied. For this propose, the third harmonic degeneration (THG) technique has been employed. A laser source has been used for the fundamental beam at 1064 nm so that the generated third harmonic signal is made at 355 nm.

Kinetics of photoluminescence of porous silicon studied by photo-luminescence excitation spectroscopy and time-resolved spectroscopy

Photoluminescence (PL) spectra and excitation spectra (PLE) (under steady-state conditions), time resolved spectra (PL-TRS) and decay curves of photoluminescence (PL-DC) in micro- and nanosecond range (under pulsed operation) at different temperatures (10 K-room) on anodically etched boron-doped silicon are presented. PLE shows that visible PL is excited by light from UV region. PL and PL-TRS exhibit multiband structure and can be decomposed as a sum of few Gaussians. PL-DCs have multiexponential shape. Relaxation times depend on wavelength of the observation. To explain our results we assumed a model in which the multibarrier structure is formed by larger Si crystallites or wires (quantum well) surrounded by Si crystallites with diameters in the nanometer range (barrier region). The visible photoluminescence originates from radiative recombination between discrete energy levels in a quantum well.

Pulsed laser deposition of hafnium oxide on quartz substrate

In this paper, we report the experimental investigation of optical properties of HfO2 (hafnium oxide) thin films grown on quartz substrates by pulsed laser deposition (PLD) method [1]. Cold pressed powders of hafnium oxide (HfO2 98% - Aldrich Chem. Co.) were used as the target for deposition process. The transparent quartz substrate was heated up to temperature in the range between 200 and 600 °C. Optical properties of the films were investigated by transmittance in the ultra-violet, visible and near infrared range and photoluminescence spectroscopy. We measure the photo-luminescence spectra and dynamics of luminescence process [2]. The PL spectra contained one strong maximum at 385 nm and the peak intensity decreases rapidly with increasing temperature. Optical properties are closely related to the structure of the hafnium oxide thin films.

Study of photoadmittance and admittance of porous silicon layers

In this work, we investigated electrical properties of Al/PS/p-Si structures. Admittance spectroscopy is one of the major semiconductor diagnostic techniques. Frequency, voltage and wavelengths dependencies of admittance will be analyzed in detail. It will be useful for better understanding of fundamental electrical properties of porous silicon.

Photoluminescence of porous silicon under pulsed excitation

Photoluminescence time resolved spectra (PL-TRS) and decay curves of photoluminescence (PL-DC) in the wavelength range 400-850 nm in micro and nanosecond time range at different temperatures (10K-room) on anodically etched boron doped porous silicon are presented. PL-TRS exhibit multiband structure and can be decomposed as a sum of few Gaussians. Positions of gaussian emission bands depend on temperature and change similar to thermal profile of the energy gap of the bulk silicon. PL-DC have multi exponential shape. Relaxation times depend on wavelength of the observation and temperature. At low temperature decay times dramatically increase (from few microsecond(s) at 300K to some hundred microsecond(s) ) and short component in nanosecond range has been observed. To explain our results we assumed model in which the multi barrier structure is formed by Si crystal (quantum well) surrounded by Si crystallites with diameters in the nanometer range (barrier region). The visible photoluminescence originates from radiative recombination between discrete energy levels in quantum well regions. Short component of decay at lowest temperatures is connected to non-radiative Auger relaxation inside porous silicon structures.

Pulsed laser deposition (PLD) of hafnium oxide thin films

This work contains the experimental investigation of optical properties of HfO2 (hafnium oxide) thin films grown on quartz and n-type silica substrates by pulsed laser deposition method. Cold pressed powders of hafnium oxide (HfO2 98% - Aldrich Chem. Co.) were used as the target for deposition process. The substrates was heated up to temperature in the range between 200 and 500 °C. Optical properties of the films were investigated by transmittance in the ultra-violet, visible and near infrared range and photoluminescence spectroscopy. We measure the photo-luminescence spectra and dynamics of luminescence process. Optical properties are closely related to the structure of the hafnium oxide thin films.

Photoluminescence of MgO thin films on Si (111) substrate, prepared by sol-gel method

Here we present the results of the measurements of photoluminescence properties of thin films of MgO (magnesium oxide) on Si substrate (mono-crystalline (111) silicon). The samples were prepared by the sol-gel method that is very simple method for fabrication metal oxide layers on different kind of substrates. We carried out the photoluminescence experiments at a wide range of temperatures from 10 to 300 K. We summarize how shape complexity of registered spectra depends on the temperature and the preparation conditions.

Investigations of temperature dependent photoluminescence process in MgO thin films

Pulsed laser deposition (PLD) technique (called also laser ablation) has been employed to grow magnesium oxide thin films on quartz wafers. The optical properties of MgO thin films were studied using temperature dependent photoluminescence measurements. The structural properties of the MgO thin films were carried out using X-ray method. A strong dependence of the films structure, the crystalline quality and the optical properties of investigated films caused by variation of substrates temperature was observed.