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Papers by Nenad Bundaleski

Progress in Photovoltaics: Research and Applications, 2015

AIP Conference Proceedings, 2004

The broad maximum in the energy spectra of Ar+ ions scattered from the clean metal surfaces to th... more The broad maximum in the energy spectra of Ar+ ions scattered from the clean metal surfaces to the scattering angles smaller than 90° is studied. Besides the Ar+ ions, other ion species (He+, N+ and Ne+) are also used as projectiles. The targets in the experiments were polycrystalline silver and copper as well as the monocrystalline nickel (110). According to

Physical Review Letters, Nov 1, 2008

Diffraction of fast atoms at grazing incidence has been recently demonstrated on the surface of a... more Diffraction of fast atoms at grazing incidence has been recently demonstrated on the surface of alkali halides and wide band gap semiconductors, opening applications for the online monitoring of surface processes such as growth of ultrathin layers. This Letter reports energy resolved diffraction of helium on Ag(110) metal surface showing that a band gap is not mandatory to restrict the decoherence due to electron-hole pair excitations by the keV projectile. Measurement of the energy loss, which is in the eV range, sheds light on the scattering process.

Materials Research Bulletin, 2016

In this paper the results of an examination of the surface roughness and morphology dependence of... more In this paper the results of an examination of the surface roughness and morphology dependence of silver thin films up to 100 nm thick deposited on a microscope glass on the deposition rate and on the deposition time are presented. It was found that, for a constant deposition rate, the surface roughness exhibits minimum at a certain layer thickness. This coincides with the turning point when the influence of the substrate surface on the deposition process becomes negligible, i.e., to the change in the nature of the system substrate/deposit from Ag/glass to Ag/Ag. For a constant layer thickness, the surface roughness minimum, achieved at a certain deposition rate, coincides to the turning point when the average free path for vertical adatom mobility becomes zero.

The W-Ti thin films are deposited by the dc Ar + sputtering of W(70%)-Ti(30%) a.t. target on sili... more The W-Ti thin films are deposited by the dc Ar + sputtering of W(70%)-Ti(30%) a.t. target on silicon substrates. The surface composition and structure of the thin film, previously exposed to air, was carried out. The surface structure was undertaken using grazing incidence X-ray diffraction (GIXRD), and compared to that of the thin film interior. The surface morphology was determined by the Scanning Tunneling Microscopy (STM). The surface composition and chemical bonding of elements on the Ti-W film were analyzed by X-ray photoelectron spectroscopy (XPS) and Low Energy Ion Scattering (LEIS). The measurements show that the overlayer of metallic oxides TiO 2 and WO 3 is formed. The first atomic layer is occupied by TiO 2 only, and its thickness is estimated to about 3.2 AE 0.4 nm. The strong surface segregation of Ti is triggered by the surface oxidation, which is confirmed by the thermodynamical considerations. #

Vacuum, 2015

Secondary electron emission plays an important role in many applications such as scanning electro... more Secondary electron emission plays an important role in many applications such as scanning electron microscopy, space applications and accelerator technologies. Secondary electron yield d(E) at normal incidence of a primary electron beam is frequently modelled by the well-known semi-empirical law. However, this model is not used in a consistent way to predict the angular dependence. Additionally, neglecting the energy reflection has particular influence on the angular dependence of the secondary electron yield and therefore cannot be ignored. We propose here a simple approach to calculate d(E) for any incident angle based on the experimental result achieved at normal incidence. The secondary electron yield is calculated according to the universal semi-empirical law, while a fraction of the electron energy deposited into the sample is calculated using a Monte Carlo simulation. A simple modification of the original model for calculating a total electron yield (i.e. the sum of the 'true' secondaries and backscattered electrons) is also presented. Very good agreement is observed between measurements and the calculation as long as the roughness is not significant. The model works very well for both, low Z and high Z materials. In the case of rough samples this approach cannot predict the angular dependence of the total electron yield.

Procedia Technology, 2014

We have studied the optimal deposition conditions for the production of low-oxygen-content Zinc n... more We have studied the optimal deposition conditions for the production of low-oxygen-content Zinc nitride films (ZnON) by Pulsed Laser Deposition (PLD). In particular, substrate temperature has been varied between 100 and 500 ºC. The film properties, particularly its morphology, showed a strong dependence on substrate temperature. Substrate temperatures beyond 350ºC led to highly crystalline and smooth films with a band gap of 3.32 eV and with resistivities ranging from 10 -2 to 100 Ωcm. Film quality and surface oxygen content changed rapidly with exposure to air as evidenced by XPS analysis.

Experimental diffraction patterns produced by grazing scattering of fast helium atoms from a Ag(1... more Experimental diffraction patterns produced by grazing scattering of fast helium atoms from a Ag(110) surface are used as a sensitive tool to test both the scattering and the potential models.

Deposition of low secondary electron yield (SEY) carbon coatings by magnetron sputtering onto the... more Deposition of low secondary electron yield (SEY) carbon coatings by magnetron sputtering onto the inner walls of the accelerator seems to be the most promising solution for suppressing the electron cloud problem. However, these coatings change their electron emission properties during long term exposure to air. The ageing process of carbon coated samples with initial SEY of about 0.9 received from CERN is studied as a function of exposure to different environments. It is shown that samples having the same initial SEY may age with different rates. The SEY increase can be correlated with the surface concentration of oxygen. Annealing of samples in air at 100-200 {\deg}C reduces the ageing rate and even recovers previously degraded samples. The result of annealing is reduction of the hydrogen content in the coatings by triggering its surface segregation followed by desorption.

ABSTRACT Diffraction problems in analytical treatments and numeric have been constant topics for ... more ABSTRACT Diffraction problems in analytical treatments and numeric have been constant topics for a very long time and there are a lot of different analytical expressions as well as numerical algorithms. The modern approaches are concentrated in the area of particle sizing, fiber optical sizing and loss evaluation in laser physics and techniques. Some problems between the fiber optics dimensioning and particles of cylindrical shape dimensioning are chosen and based on literature; some ameliorations in numerical approaches are made. The evolved expressions can be used for different laser wavelengths, different dimensions of disturbance objects (in scattering and diffraction phenomena) as well as different indices of refractions where the particles (in a very general way) are stratified. Some existing programs for scattering are discussed and the new computer architecture is presented here.

... 20. E. Michielssen, S. Ranjithan and R. Mittra, IEE Proceedings J, 139(12), 413, (1992). 21. ... more ... 20. E. Michielssen, S. Ranjithan and R. Mittra, IEE Proceedings J, 139(12), 413, (1992). 21. S.Martin, J. Rivory and M. Shoenauer, Opt. Comm,110,503,(1994). 22. T. Eisenhammer, M. Lazarov, M. Leutbecher, U. Schoeffel and R. Sizmann, Appl. Opt., 32, 6310, (1994). 23. ...

Progress in Photovoltaics: Research and Applications, 2015

AIP Conference Proceedings, 2004

The broad maximum in the energy spectra of Ar+ ions scattered from the clean metal surfaces to th... more The broad maximum in the energy spectra of Ar+ ions scattered from the clean metal surfaces to the scattering angles smaller than 90° is studied. Besides the Ar+ ions, other ion species (He+, N+ and Ne+) are also used as projectiles. The targets in the experiments were polycrystalline silver and copper as well as the monocrystalline nickel (110). According to

Physical Review Letters, Nov 1, 2008

Diffraction of fast atoms at grazing incidence has been recently demonstrated on the surface of a... more Diffraction of fast atoms at grazing incidence has been recently demonstrated on the surface of alkali halides and wide band gap semiconductors, opening applications for the online monitoring of surface processes such as growth of ultrathin layers. This Letter reports energy resolved diffraction of helium on Ag(110) metal surface showing that a band gap is not mandatory to restrict the decoherence due to electron-hole pair excitations by the keV projectile. Measurement of the energy loss, which is in the eV range, sheds light on the scattering process.

Materials Research Bulletin, 2016

In this paper the results of an examination of the surface roughness and morphology dependence of... more In this paper the results of an examination of the surface roughness and morphology dependence of silver thin films up to 100 nm thick deposited on a microscope glass on the deposition rate and on the deposition time are presented. It was found that, for a constant deposition rate, the surface roughness exhibits minimum at a certain layer thickness. This coincides with the turning point when the influence of the substrate surface on the deposition process becomes negligible, i.e., to the change in the nature of the system substrate/deposit from Ag/glass to Ag/Ag. For a constant layer thickness, the surface roughness minimum, achieved at a certain deposition rate, coincides to the turning point when the average free path for vertical adatom mobility becomes zero.

The W-Ti thin films are deposited by the dc Ar + sputtering of W(70%)-Ti(30%) a.t. target on sili... more The W-Ti thin films are deposited by the dc Ar + sputtering of W(70%)-Ti(30%) a.t. target on silicon substrates. The surface composition and structure of the thin film, previously exposed to air, was carried out. The surface structure was undertaken using grazing incidence X-ray diffraction (GIXRD), and compared to that of the thin film interior. The surface morphology was determined by the Scanning Tunneling Microscopy (STM). The surface composition and chemical bonding of elements on the Ti-W film were analyzed by X-ray photoelectron spectroscopy (XPS) and Low Energy Ion Scattering (LEIS). The measurements show that the overlayer of metallic oxides TiO 2 and WO 3 is formed. The first atomic layer is occupied by TiO 2 only, and its thickness is estimated to about 3.2 AE 0.4 nm. The strong surface segregation of Ti is triggered by the surface oxidation, which is confirmed by the thermodynamical considerations. #

Vacuum, 2015

Secondary electron emission plays an important role in many applications such as scanning electro... more Secondary electron emission plays an important role in many applications such as scanning electron microscopy, space applications and accelerator technologies. Secondary electron yield d(E) at normal incidence of a primary electron beam is frequently modelled by the well-known semi-empirical law. However, this model is not used in a consistent way to predict the angular dependence. Additionally, neglecting the energy reflection has particular influence on the angular dependence of the secondary electron yield and therefore cannot be ignored. We propose here a simple approach to calculate d(E) for any incident angle based on the experimental result achieved at normal incidence. The secondary electron yield is calculated according to the universal semi-empirical law, while a fraction of the electron energy deposited into the sample is calculated using a Monte Carlo simulation. A simple modification of the original model for calculating a total electron yield (i.e. the sum of the 'true' secondaries and backscattered electrons) is also presented. Very good agreement is observed between measurements and the calculation as long as the roughness is not significant. The model works very well for both, low Z and high Z materials. In the case of rough samples this approach cannot predict the angular dependence of the total electron yield.

Procedia Technology, 2014

We have studied the optimal deposition conditions for the production of low-oxygen-content Zinc n... more We have studied the optimal deposition conditions for the production of low-oxygen-content Zinc nitride films (ZnON) by Pulsed Laser Deposition (PLD). In particular, substrate temperature has been varied between 100 and 500 ºC. The film properties, particularly its morphology, showed a strong dependence on substrate temperature. Substrate temperatures beyond 350ºC led to highly crystalline and smooth films with a band gap of 3.32 eV and with resistivities ranging from 10 -2 to 100 Ωcm. Film quality and surface oxygen content changed rapidly with exposure to air as evidenced by XPS analysis.

Experimental diffraction patterns produced by grazing scattering of fast helium atoms from a Ag(1... more Experimental diffraction patterns produced by grazing scattering of fast helium atoms from a Ag(110) surface are used as a sensitive tool to test both the scattering and the potential models.

Deposition of low secondary electron yield (SEY) carbon coatings by magnetron sputtering onto the... more Deposition of low secondary electron yield (SEY) carbon coatings by magnetron sputtering onto the inner walls of the accelerator seems to be the most promising solution for suppressing the electron cloud problem. However, these coatings change their electron emission properties during long term exposure to air. The ageing process of carbon coated samples with initial SEY of about 0.9 received from CERN is studied as a function of exposure to different environments. It is shown that samples having the same initial SEY may age with different rates. The SEY increase can be correlated with the surface concentration of oxygen. Annealing of samples in air at 100-200 {\deg}C reduces the ageing rate and even recovers previously degraded samples. The result of annealing is reduction of the hydrogen content in the coatings by triggering its surface segregation followed by desorption.

ABSTRACT Diffraction problems in analytical treatments and numeric have been constant topics for ... more ABSTRACT Diffraction problems in analytical treatments and numeric have been constant topics for a very long time and there are a lot of different analytical expressions as well as numerical algorithms. The modern approaches are concentrated in the area of particle sizing, fiber optical sizing and loss evaluation in laser physics and techniques. Some problems between the fiber optics dimensioning and particles of cylindrical shape dimensioning are chosen and based on literature; some ameliorations in numerical approaches are made. The evolved expressions can be used for different laser wavelengths, different dimensions of disturbance objects (in scattering and diffraction phenomena) as well as different indices of refractions where the particles (in a very general way) are stratified. Some existing programs for scattering are discussed and the new computer architecture is presented here.

... 20. E. Michielssen, S. Ranjithan and R. Mittra, IEE Proceedings J, 139(12), 413, (1992). 21. ... more ... 20. E. Michielssen, S. Ranjithan and R. Mittra, IEE Proceedings J, 139(12), 413, (1992). 21. S.Martin, J. Rivory and M. Shoenauer, Opt. Comm,110,503,(1994). 22. T. Eisenhammer, M. Lazarov, M. Leutbecher, U. Schoeffel and R. Sizmann, Appl. Opt., 32, 6310, (1994). 23. ...