Stanislav Voborny | Brno University of Technology (original) (raw)

Papers by Stanislav Voborny

Applied Surface Science, 2019

Review of Scientific Instruments, 2014

We describe the optimization and application of an ion-atomic beam source for ion-beam-assisted d... more We describe the optimization and application of an ion-atomic beam source for ion-beam-assisted deposition of ultrathin films in ultrahigh vacuum. The device combines an effusion cell and electron-impact ion beam source to produce ultra-low energy (20-200 eV) ion beams and thermal atomic beams simultaneously. The source was equipped with a focusing system of electrostatic electrodes increasing the maximum nitrogen ion current density in the beam of a diameter of ≈15 mm by one order of magnitude (j ≈ 1000 nA/cm(2)). Hence, a successful growth of GaN ultrathin films on Si(111) 7 × 7 substrate surfaces at reasonable times and temperatures significantly lower (RT, 300 °C) than in conventional metalorganic chemical vapor deposition technologies (≈1000 °C) was achieved. The chemical composition of these films was characterized in situ by X-ray Photoelectron Spectroscopy and morphology ex situ using Scanning Electron Microscopy. It has been shown that the morphology of GaN layers strongly depends on the relative Ga-N bond concentration in the layers.

Thin Solid Films, 2004

In the paper the application of a complex UHV apparatus for in-situ investigation of low-temperat... more In the paper the application of a complex UHV apparatus for in-situ investigation of low-temperature Ga-N ultra-thin film synthesis by thermal Ga atoms and hyperthermal nitrogen ions is presented. It was found by XPS that the highest content of Ga-N bonds was present in the layers grown on a 'nitrogen-rich' substrate at enhanced substrate temperature (400 8C). 'Nitrogenrich' Si surfaces grew from hyperthermal nitrogen ions on substrates contaminated by oxygen ('native' and chemically etched Si). The 'gallium-rich' substrate possessed smaller number of Ga-N bonds. Higher content of Ga-O bonds was found on Si substrates covered by native oxide and chemically etched silicon. Due to low nitrogen ion currents the thickness of the films was small (-4 ML). ᮊ

Surface Science, 2007

Results for deposition and thermal annealing of gallium on the Si(1 0 0)-(2 · 1) surface achieved... more Results for deposition and thermal annealing of gallium on the Si(1 0 0)-(2 · 1) surface achieved by synchrotron radiation photoelectron spectroscopy (SR-PES) and low energy electron diffraction (LEED) are presented. In addition to deposition of Ga on a clean surface, the influence of water adsorption on the arrangement of gallium atoms was also studied. The results on Ga deposition at a higher temperature (490°C) are consistent with a Ga ad-dimer model showing equivalent bond arrangement of all Ga atoms for coverages up to 0.5 ML. The deposition onto a surface with adsorbed water at room temperature led to a disordered gallium growth. In this case gallium atoms bind to silicon dimers already binding fragments of adsorbed water. A subsequent annealing of these layers leads to a surface structure similar to the Ga-(2 · 2), however, it is less ordered, probably due to the presence of silicon oxides formed from water fragments.

Review of Scientific Instruments, 2011

The paper describes the design and construction of an ion-atomic beam source with an optimized ge... more The paper describes the design and construction of an ion-atomic beam source with an optimized generation of ions for ion-beam-assisted deposition under ultrahigh vacuum (UHV) conditions. The source combines an effusion cell and an electron impact ion source and produces ion beams with ultra-low energies in the range from 30 eV to 200 eV. Decreasing ion beam energy to hyperthermal values (≈10(1) eV) without loosing optimum ionization conditions has been mainly achieved by the incorporation of an ionization chamber with a grid transparent enough for electron and ion beams. In this way the energy and current density of nitrogen ion beams in the order of 10(1) eV and 10(1) nA/cm(2), respectively, have been achieved. The source is capable of growing ultrathin layers or nanostructures at ultra-low energies with a growth rate of several MLs/h. The ion-atomic beam source will be preferentially applied for the synthesis of GaN under UHV conditions.

Review of Scientific Instruments, 2014

We describe the optimization and application of an ion-atomic beam source for ion-beam-assisted d... more We describe the optimization and application of an ion-atomic beam source for ion-beam-assisted deposition of ultrathin films in ultrahigh vacuum. The device combines an effusion cell and electron-impact ion beam source to produce ultra-low energy (20-200 eV) ion beams and thermal atomic beams simultaneously. The source was equipped with a focusing system of electrostatic electrodes increasing the maximum nitrogen ion current density in the beam of a diameter of ≈15 mm by one order of magnitude (j ≈ 1000 nA/cm(2)). Hence, a successful growth of GaN ultrathin films on Si(111) 7 × 7 substrate surfaces at reasonable times and temperatures significantly lower (RT, 300 °C) than in conventional metalorganic chemical vapor deposition technologies (≈1000 °C) was achieved. The chemical composition of these films was characterized in situ by X-ray Photoelectron Spectroscopy and morphology ex situ using Scanning Electron Microscopy. It has been shown that the morphology of GaN layers strongly depends on the relative Ga-N bond concentration in the layers.

Applied Surface Science, 2019

Review of Scientific Instruments, 2014

We describe the optimization and application of an ion-atomic beam source for ion-beam-assisted d... more We describe the optimization and application of an ion-atomic beam source for ion-beam-assisted deposition of ultrathin films in ultrahigh vacuum. The device combines an effusion cell and electron-impact ion beam source to produce ultra-low energy (20-200 eV) ion beams and thermal atomic beams simultaneously. The source was equipped with a focusing system of electrostatic electrodes increasing the maximum nitrogen ion current density in the beam of a diameter of ≈15 mm by one order of magnitude (j ≈ 1000 nA/cm(2)). Hence, a successful growth of GaN ultrathin films on Si(111) 7 × 7 substrate surfaces at reasonable times and temperatures significantly lower (RT, 300 °C) than in conventional metalorganic chemical vapor deposition technologies (≈1000 °C) was achieved. The chemical composition of these films was characterized in situ by X-ray Photoelectron Spectroscopy and morphology ex situ using Scanning Electron Microscopy. It has been shown that the morphology of GaN layers strongly depends on the relative Ga-N bond concentration in the layers.

Thin Solid Films, 2004

In the paper the application of a complex UHV apparatus for in-situ investigation of low-temperat... more In the paper the application of a complex UHV apparatus for in-situ investigation of low-temperature Ga-N ultra-thin film synthesis by thermal Ga atoms and hyperthermal nitrogen ions is presented. It was found by XPS that the highest content of Ga-N bonds was present in the layers grown on a 'nitrogen-rich' substrate at enhanced substrate temperature (400 8C). 'Nitrogenrich' Si surfaces grew from hyperthermal nitrogen ions on substrates contaminated by oxygen ('native' and chemically etched Si). The 'gallium-rich' substrate possessed smaller number of Ga-N bonds. Higher content of Ga-O bonds was found on Si substrates covered by native oxide and chemically etched silicon. Due to low nitrogen ion currents the thickness of the films was small (-4 ML). ᮊ

Surface Science, 2007

Results for deposition and thermal annealing of gallium on the Si(1 0 0)-(2 · 1) surface achieved... more Results for deposition and thermal annealing of gallium on the Si(1 0 0)-(2 · 1) surface achieved by synchrotron radiation photoelectron spectroscopy (SR-PES) and low energy electron diffraction (LEED) are presented. In addition to deposition of Ga on a clean surface, the influence of water adsorption on the arrangement of gallium atoms was also studied. The results on Ga deposition at a higher temperature (490°C) are consistent with a Ga ad-dimer model showing equivalent bond arrangement of all Ga atoms for coverages up to 0.5 ML. The deposition onto a surface with adsorbed water at room temperature led to a disordered gallium growth. In this case gallium atoms bind to silicon dimers already binding fragments of adsorbed water. A subsequent annealing of these layers leads to a surface structure similar to the Ga-(2 · 2), however, it is less ordered, probably due to the presence of silicon oxides formed from water fragments.

Review of Scientific Instruments, 2011

The paper describes the design and construction of an ion-atomic beam source with an optimized ge... more The paper describes the design and construction of an ion-atomic beam source with an optimized generation of ions for ion-beam-assisted deposition under ultrahigh vacuum (UHV) conditions. The source combines an effusion cell and an electron impact ion source and produces ion beams with ultra-low energies in the range from 30 eV to 200 eV. Decreasing ion beam energy to hyperthermal values (≈10(1) eV) without loosing optimum ionization conditions has been mainly achieved by the incorporation of an ionization chamber with a grid transparent enough for electron and ion beams. In this way the energy and current density of nitrogen ion beams in the order of 10(1) eV and 10(1) nA/cm(2), respectively, have been achieved. The source is capable of growing ultrathin layers or nanostructures at ultra-low energies with a growth rate of several MLs/h. The ion-atomic beam source will be preferentially applied for the synthesis of GaN under UHV conditions.

Review of Scientific Instruments, 2014

We describe the optimization and application of an ion-atomic beam source for ion-beam-assisted d... more We describe the optimization and application of an ion-atomic beam source for ion-beam-assisted deposition of ultrathin films in ultrahigh vacuum. The device combines an effusion cell and electron-impact ion beam source to produce ultra-low energy (20-200 eV) ion beams and thermal atomic beams simultaneously. The source was equipped with a focusing system of electrostatic electrodes increasing the maximum nitrogen ion current density in the beam of a diameter of ≈15 mm by one order of magnitude (j ≈ 1000 nA/cm(2)). Hence, a successful growth of GaN ultrathin films on Si(111) 7 × 7 substrate surfaces at reasonable times and temperatures significantly lower (RT, 300 °C) than in conventional metalorganic chemical vapor deposition technologies (≈1000 °C) was achieved. The chemical composition of these films was characterized in situ by X-ray Photoelectron Spectroscopy and morphology ex situ using Scanning Electron Microscopy. It has been shown that the morphology of GaN layers strongly depends on the relative Ga-N bond concentration in the layers.