Jan Ivanco | Slovak Academy of Sciences (original) (raw)
Papers by Jan Ivanco
Thin Solid Films, 2016
The strain-resistance transduction of commercially available In 2 O 3 /Au/Ag layered films suppor... more The strain-resistance transduction of commercially available In 2 O 3 /Au/Ag layered films supported by polyethylene terephthalate (PET) foil was studied. A colossal gauge factor as high as about 60 000 was observed upon a strain of 1 %. Such ultra-high response is presumably owing to conductivity derived from the tunnelling current across cracks formed in the strained In 2 O 3 film; the cracks-as visualized by scanning electron microscopy-are oriented perpendicularly to the strain vector and are noted for their uniform width across the sample. It is further demonstrated that the standardly defined gauge factor is incommensurate for strain sensors with transduction based on the tunnelling current and a redefined formula for the gauge factor was proposed.
Organic Electronics, 2004
The epitaxial growth of sexiphenyl (C 36 H 26) on an atomically clean aluminium (1 1 1) surface i... more The epitaxial growth of sexiphenyl (C 36 H 26) on an atomically clean aluminium (1 1 1) surface is studied on the basis of thin films grown at different substrate temperatures. Thin films with an average thickness of 350 A are investigated by X-ray diffraction techniques and atomic force microscopy. Grown at room temperature the films show epitaxial order. It is found that the aromatic planes of sexiphenyl are oriented parallel to Al(1 1 1) and the long axes of the sexiphenyl molecules are aligned along a AE1)1 0ae azimuthal direction at the Al(1 1 1) surface. The films grow in islands with average lateral dimensions up to of 200 nm and to 50 nm in height, the areas between the islands are observed as rather flat. The films grown at 150°C show a completely different morphology: occasional large islands and irregularly distributed segmented needles with a relatively constant width of about 0.5 lm, lengths up to 100 lm and heights of about 600 nm. Although the film appears as crystalline, no epitaxy could be verified.
Organic Electronics, 2007
The electronic level alignment of the organic semiconductor para-sexiphenyl on a nanoscopically p... more The electronic level alignment of the organic semiconductor para-sexiphenyl on a nanoscopically patterned substrate was investigated with ultraviolet photoemission spectroscopy, work function measurements and scanning tunnelling microscopy. The results show that for increasing coverage on inhomogeneous surfaces, shifts in electronic level alignment occur, which are due to the change from local to average band alignment. The Cu(110)–(2×1)O stripe phase, used
Physical Chemistry Chemical Physics
The ability to control the interparticle distance in self-assembled arrays of nanoparticles plays... more The ability to control the interparticle distance in self-assembled arrays of nanoparticles plays an important role in a large number of applications, which require tunable electronic and photonic properties. Importantly,...
ABSTRACT A method of observation of interface states for ultrathin insulating layer/semiconductor... more ABSTRACT A method of observation of interface states for ultrathin insulating layer/semiconductor interfaces is developed by use of X-ray photoelectron spectroscopy (XPS) measurements under bias. The analysis of the energy shift of the semiconductor core level as a function of the bias voltage gives energy distribution of interface states. When the atomic density of SiO2 layers is low (e.g., SiO2 layers formed at 350 °C), only one interface state peak is observed near the midgap, and it is attributed to isolated Si dangling bonds at the interface. For SiO2 layers with a high atomic density (e.g., SiO2 layers formed at 700 °C), on the other hand, two interface state peaks, one above and the other below the midgap, are observed, and they are attributed to Si dangling bonds interacting weakly with a Si or oxygen atom in SiO2. Interface states can be passivated by cyanide treatment which simply involves the immersion in cyanide solutions such as KCN and HCN solutions. When the cyanide treatment is applied to 〈indium tin oxide/SiO2/mat-textured single crystalline Si〉 metal-oxide-semiconductor (MOS) solar cells, the photovoltage is greatly increased, leading to a high conversion efficiency of 16.2%. When the cyanide treatment is performed on polycrystalline Si (poly-Si)-based MOS diodes, a greater effect in comparison to that for single crystalline Si-based MOS diodes is observed due to the elimination of defect states in poly-Si as well as Si/SiO2 interface states. The cyanide treatment can also increase the conversion efficiency of pn-junction single crystalline and poly-Si solar cells.
APPLIED PHYSICS OF CONDENSED MATTER (APCOM 2019)
The paper reviews the state of the art of graphene employed as an active layer in chemiresistive ... more The paper reviews the state of the art of graphene employed as an active layer in chemiresistive gas sensors. Graphene properties such as high specific surface area, low noise, planar structure, flexibility, etc., are commonly highlighted as strengths in the sensors technology. However, the listed virtues are mostly related to the pristine graphene or even graphene monolayers, while majority of devices use chemically synthesized graphene derivatives. These vague statements may be induced by the high level of graphene hype and racing for the research grants. Moreover, graphene has no dangling bonds functioning as prime reaction agents. This led us to propose more adequate view onto a capacity of graphene in the area of gas sensors. In this study, we focused onto three aspects: (i) the substantiation of the low noise for sensing devices, (ii) the assumed versus actual surface area of the real graphene layers, and (iii) an integration of graphene sensors into silicon circuits.
Measurement Science Review
NO2 and H2 gas sensing by few-layer graphene (FLG) were studied in dependence on the annealing an... more NO2 and H2 gas sensing by few-layer graphene (FLG) were studied in dependence on the annealing and decoration of graphene by palladium nanoparticles (NPs). Graphene was deposited onto SiO2 (500 nm)/Si substrates by a modified Langmuir-Schaefer technique. A solution of FLG flakes in 1-methyl-2-pyrrolidone was obtained by a mild sonication of the expanded milled graphite. FLG films were characterized by atomic force microscopy, X-ray diffraction, Raman spectroscopy, and the Brunnauer-Emmett-Teller method. Average FLG flake thickness and lateral dimension were 5 nm and 300 nm, respectively. Drop casting of Pd NP (6–7 nm) solution onto FLG film was applied to decorate graphene by Pd. The room temperature (RT) resistance of the samples was stabilized at 15 kΩ by vacuum annealing. Heating cycles of FLG film revealed its semiconducting character. The gas sensing was tested in the mixtures of dry air with H2 gas (10 to 10 000 ppm) and NO2 gas (2 to 200 ppm) between RT and 200 °C. The respon...
Procedia Engineering, 2016
Org Electron, 2007
The growth of sexithiophene ultra-thin films on an atomically clean Al(1 1 1) surface has been in... more The growth of sexithiophene ultra-thin films on an atomically clean Al(1 1 1) surface has been investigated by angleresolved ultraviolet photoemission spectroscopy. Although sexithiophene on Al(1 1 1) represents a weakly interacting system, sexithiophene molecules were found to dissociate even below room temperature, presumably via reactive sites. The mechanism is distinctly different to that claimed on the reverse system, i.e. aluminum evaporated on thiophene oligomers films, where isolated aluminum atoms were reported to covalently bond to thiophene rings and thus dramatically affect the molecule geometry and the conjugation. The effect of the insertion of an ultra-thin separator film of sexiphenyl, on the dissociation of sexithiophene was also examined.
J Cryst Growth, 2008
This is a report on sexithiophene thin films (6-300 Å ) grown on TiO 2 (1 1 0) single crystal sur... more This is a report on sexithiophene thin films (6-300 Å ) grown on TiO 2 (1 1 0) single crystal surfaces. The films are investigated by atomic force microscopy and both laboratory and synchrotron X-ray diffraction techniques. Different growth stages are identified: after the formation of a first lying monolayer, small clusters are formed. Thicker films show needle like morphologies with two distinct needle directions. The morphology can be assigned to the obtained crystal alignments and a growth model is derived: the oxygen rows of the surface direct the alignment of initially adsorbed molecules parallel to the surface corrugation. Further molecules form small clusters on top of this monolayer. At a sufficient cluster size they merge and crystallize in the so-called low temperature phase with the contact plane {0 1 0} having a mosaicity of 1-2 . Furthermore, the observed crystallites show a distinct in-plane alignment, with a distribution of few degrees which perfectly explains the two needle directions. However, the molecules of the crystallites are slightly rotated to the oxygen rows, which is ascribed to a lattice match effect. Therefore it is concluded that the molecules of the monolayer are integrated in the crystal structure and undergo a slight realignment during 3D crystal growth. Finally the importance of an atomically ordered substrate surface is illustrated by a comparison to a film grown on an intentionally disordered surface leading to standing molecules without in-plane order. r
Sensor Letters, 2013
The Fe 2 O 3 and CoFe 2 O 4 nanoparticle-based Langmuir-Blodgett films for sensing of nitric diox... more The Fe 2 O 3 and CoFe 2 O 4 nanoparticle-based Langmuir-Blodgett films for sensing of nitric dioxide (NO 2 ) and acetone vapours have been explored. Both the sensitivity of the chemiresistors and dynamic properties, such as the response/recovery time, have been probed in dependence of the number of nanoparticle monolayers and working temperatures. The response of 23 at the NO 2 concentration of 1 ppm, i.e., approaching the canine detection limit, has been monitored implying the appropriateness for the detection of nitrate-based explosives. monolayers and thereby the controlled formation of the sensing film with targeted number of monolayers enabling to explore the effect of the film thickness on sensing properties.
Organic Electronics, 2007
The growth of sexithiophene ultra-thin films on an atomically clean Al(1 1 1) surface has been in... more The growth of sexithiophene ultra-thin films on an atomically clean Al(1 1 1) surface has been investigated by angleresolved ultraviolet photoemission spectroscopy. Although sexithiophene on Al(1 1 1) represents a weakly interacting system, sexithiophene molecules were found to dissociate even below room temperature, presumably via reactive sites. The mechanism is distinctly different to that claimed on the reverse system, i.e. aluminum evaporated on thiophene oligomers films, where isolated aluminum atoms were reported to covalently bond to thiophene rings and thus dramatically affect the molecule geometry and the conjugation. The effect of the insertion of an ultra-thin separator film of sexiphenyl, on the dissociation of sexithiophene was also examined.
Key Engineering Materials, 2014
The Fe2O3 and CoFe2O4 nanoparticle-based Langmuir-Blodgett lms for sensingof nitrogen dioxide (NO... more The Fe2O3 and CoFe2O4 nanoparticle-based Langmuir-Blodgett lms for sensingof nitrogen dioxide (NO2) and acetone vapours have been explored. Both the sensitivity of thechemiresistors and dynamic properties, such as the response/recovery time, have been probed independence of the number of nanoparticle monolayers and working temperatures. The responseof 23 at the NO2 concentration of 1 ppm has been monitored suggesting the pertinent sensitivityin the deep sub-ppm range, i.e. approaching the canine detection limit, and likewise implyingthe supposable detection of nitrate-based explosives.
Organic Electronics, 2007
The electronic level alignment of the organic semiconductor para-sexiphenyl on a nanoscopically p... more The electronic level alignment of the organic semiconductor para-sexiphenyl on a nanoscopically patterned substrate was investigated with ultraviolet photoemission spectroscopy, work function measurements and scanning tunnelling microscopy. The results show that for increasing coverage on inhomogeneous surfaces, shifts in electronic level alignment occur, which are due to the change from local to average band alignment. The Cu(1 1 0)-(2 · 1)O stripe phase, used as a model substrate consists of alternating stripes of bare and oxygen passivated copper, with stripe widths of $35 Å comparable to the sexiphenyl molecular length. In the first molecular layer the electronic bands are clearly aligned to the local surface potential of the specific stripe, resulting in the superposition of two photoemission spectra offset by 1 eV. Beyond two monolayers the valence band spectra clearly indicate a single electronic level alignment, which is determined by the average interface dipole.
Vacuum, 1998
This work reports on the X-ray photoemission spectroscopy (XPS) measurements of the As-rich GaAs(... more This work reports on the X-ray photoemission spectroscopy (XPS) measurements of the As-rich GaAs(001) surface properties developing due to the different thicknesses of the undoped silicon overlayers. We analyzed the bond nature on the silicon–GaAs interface depending on the silicon thickness which was connected with observed variations in surface Fermi level positions. Further, the Au\Si\n-GaAs metal-semiconductor contacts were prepared on
Thin Solid Films, 2012
ABSTRACT The electronic properties of molecular films are analysed with the consideration of the ... more ABSTRACT The electronic properties of molecular films are analysed with the consideration of the molecular orientation. The study demonstrates that surfaces of electroactive oligomeric molecular films can be classified—analogously to the elemental surfaces—by their intrinsic work functions. The intrinsic work function of molecular films is correlated with their ionisation energies; again, the behaviour is analogous to the correlation existing between the first ionisation energy of elements and the work function of the corresponding elemental surfaces. The proposed intrinsic work-function concept suggests that the mechanism for the energy-level alignment at the interfaces associated with molecular films is virtually controlled by work functions of materials brought into the contact.
Thin Solid Films, 2003
We present a study on electrical properties of AlySi N ySiyGaAs structure studied by deep level t... more We present a study on electrical properties of AlySi N ySiyGaAs structure studied by deep level transient spectroscopy and 3 4 capacitance-voltage technique. Here, the Si means an ultrathin silicon layer with thickness of approximately 2 nm. We have modelled the presented structure, while emissions from deep levels at SiyGaAs interface, traps in the bulk of GaAs and from a quantum well (QW) possibly formed by the Si interlayer, were taken into the account. Four deep traps were identified in the structure with the following thermal activation energies: 0.04, 0.19, 0.40 and 0.68 eV. The energy levels 0.4 and 0.68 are related with As defects, while the energy levels 0.04 and 0.19 are associated with the presence of the Si interlayer. Based on the emission behaviour, an existence of the QW is not probable (can be excluded). Rather, parameters of the Si-related energy levels suggest the levels are induced by d-doping of GaAs. ᮊ
Thin Solid Films, 2016
The strain-resistance transduction of commercially available In 2 O 3 /Au/Ag layered films suppor... more The strain-resistance transduction of commercially available In 2 O 3 /Au/Ag layered films supported by polyethylene terephthalate (PET) foil was studied. A colossal gauge factor as high as about 60 000 was observed upon a strain of 1 %. Such ultra-high response is presumably owing to conductivity derived from the tunnelling current across cracks formed in the strained In 2 O 3 film; the cracks-as visualized by scanning electron microscopy-are oriented perpendicularly to the strain vector and are noted for their uniform width across the sample. It is further demonstrated that the standardly defined gauge factor is incommensurate for strain sensors with transduction based on the tunnelling current and a redefined formula for the gauge factor was proposed.
Organic Electronics, 2004
The epitaxial growth of sexiphenyl (C 36 H 26) on an atomically clean aluminium (1 1 1) surface i... more The epitaxial growth of sexiphenyl (C 36 H 26) on an atomically clean aluminium (1 1 1) surface is studied on the basis of thin films grown at different substrate temperatures. Thin films with an average thickness of 350 A are investigated by X-ray diffraction techniques and atomic force microscopy. Grown at room temperature the films show epitaxial order. It is found that the aromatic planes of sexiphenyl are oriented parallel to Al(1 1 1) and the long axes of the sexiphenyl molecules are aligned along a AE1)1 0ae azimuthal direction at the Al(1 1 1) surface. The films grow in islands with average lateral dimensions up to of 200 nm and to 50 nm in height, the areas between the islands are observed as rather flat. The films grown at 150°C show a completely different morphology: occasional large islands and irregularly distributed segmented needles with a relatively constant width of about 0.5 lm, lengths up to 100 lm and heights of about 600 nm. Although the film appears as crystalline, no epitaxy could be verified.
Organic Electronics, 2007
The electronic level alignment of the organic semiconductor para-sexiphenyl on a nanoscopically p... more The electronic level alignment of the organic semiconductor para-sexiphenyl on a nanoscopically patterned substrate was investigated with ultraviolet photoemission spectroscopy, work function measurements and scanning tunnelling microscopy. The results show that for increasing coverage on inhomogeneous surfaces, shifts in electronic level alignment occur, which are due to the change from local to average band alignment. The Cu(110)–(2×1)O stripe phase, used
Physical Chemistry Chemical Physics
The ability to control the interparticle distance in self-assembled arrays of nanoparticles plays... more The ability to control the interparticle distance in self-assembled arrays of nanoparticles plays an important role in a large number of applications, which require tunable electronic and photonic properties. Importantly,...
ABSTRACT A method of observation of interface states for ultrathin insulating layer/semiconductor... more ABSTRACT A method of observation of interface states for ultrathin insulating layer/semiconductor interfaces is developed by use of X-ray photoelectron spectroscopy (XPS) measurements under bias. The analysis of the energy shift of the semiconductor core level as a function of the bias voltage gives energy distribution of interface states. When the atomic density of SiO2 layers is low (e.g., SiO2 layers formed at 350 °C), only one interface state peak is observed near the midgap, and it is attributed to isolated Si dangling bonds at the interface. For SiO2 layers with a high atomic density (e.g., SiO2 layers formed at 700 °C), on the other hand, two interface state peaks, one above and the other below the midgap, are observed, and they are attributed to Si dangling bonds interacting weakly with a Si or oxygen atom in SiO2. Interface states can be passivated by cyanide treatment which simply involves the immersion in cyanide solutions such as KCN and HCN solutions. When the cyanide treatment is applied to 〈indium tin oxide/SiO2/mat-textured single crystalline Si〉 metal-oxide-semiconductor (MOS) solar cells, the photovoltage is greatly increased, leading to a high conversion efficiency of 16.2%. When the cyanide treatment is performed on polycrystalline Si (poly-Si)-based MOS diodes, a greater effect in comparison to that for single crystalline Si-based MOS diodes is observed due to the elimination of defect states in poly-Si as well as Si/SiO2 interface states. The cyanide treatment can also increase the conversion efficiency of pn-junction single crystalline and poly-Si solar cells.
APPLIED PHYSICS OF CONDENSED MATTER (APCOM 2019)
The paper reviews the state of the art of graphene employed as an active layer in chemiresistive ... more The paper reviews the state of the art of graphene employed as an active layer in chemiresistive gas sensors. Graphene properties such as high specific surface area, low noise, planar structure, flexibility, etc., are commonly highlighted as strengths in the sensors technology. However, the listed virtues are mostly related to the pristine graphene or even graphene monolayers, while majority of devices use chemically synthesized graphene derivatives. These vague statements may be induced by the high level of graphene hype and racing for the research grants. Moreover, graphene has no dangling bonds functioning as prime reaction agents. This led us to propose more adequate view onto a capacity of graphene in the area of gas sensors. In this study, we focused onto three aspects: (i) the substantiation of the low noise for sensing devices, (ii) the assumed versus actual surface area of the real graphene layers, and (iii) an integration of graphene sensors into silicon circuits.
Measurement Science Review
NO2 and H2 gas sensing by few-layer graphene (FLG) were studied in dependence on the annealing an... more NO2 and H2 gas sensing by few-layer graphene (FLG) were studied in dependence on the annealing and decoration of graphene by palladium nanoparticles (NPs). Graphene was deposited onto SiO2 (500 nm)/Si substrates by a modified Langmuir-Schaefer technique. A solution of FLG flakes in 1-methyl-2-pyrrolidone was obtained by a mild sonication of the expanded milled graphite. FLG films were characterized by atomic force microscopy, X-ray diffraction, Raman spectroscopy, and the Brunnauer-Emmett-Teller method. Average FLG flake thickness and lateral dimension were 5 nm and 300 nm, respectively. Drop casting of Pd NP (6–7 nm) solution onto FLG film was applied to decorate graphene by Pd. The room temperature (RT) resistance of the samples was stabilized at 15 kΩ by vacuum annealing. Heating cycles of FLG film revealed its semiconducting character. The gas sensing was tested in the mixtures of dry air with H2 gas (10 to 10 000 ppm) and NO2 gas (2 to 200 ppm) between RT and 200 °C. The respon...
Procedia Engineering, 2016
Org Electron, 2007
The growth of sexithiophene ultra-thin films on an atomically clean Al(1 1 1) surface has been in... more The growth of sexithiophene ultra-thin films on an atomically clean Al(1 1 1) surface has been investigated by angleresolved ultraviolet photoemission spectroscopy. Although sexithiophene on Al(1 1 1) represents a weakly interacting system, sexithiophene molecules were found to dissociate even below room temperature, presumably via reactive sites. The mechanism is distinctly different to that claimed on the reverse system, i.e. aluminum evaporated on thiophene oligomers films, where isolated aluminum atoms were reported to covalently bond to thiophene rings and thus dramatically affect the molecule geometry and the conjugation. The effect of the insertion of an ultra-thin separator film of sexiphenyl, on the dissociation of sexithiophene was also examined.
J Cryst Growth, 2008
This is a report on sexithiophene thin films (6-300 Å ) grown on TiO 2 (1 1 0) single crystal sur... more This is a report on sexithiophene thin films (6-300 Å ) grown on TiO 2 (1 1 0) single crystal surfaces. The films are investigated by atomic force microscopy and both laboratory and synchrotron X-ray diffraction techniques. Different growth stages are identified: after the formation of a first lying monolayer, small clusters are formed. Thicker films show needle like morphologies with two distinct needle directions. The morphology can be assigned to the obtained crystal alignments and a growth model is derived: the oxygen rows of the surface direct the alignment of initially adsorbed molecules parallel to the surface corrugation. Further molecules form small clusters on top of this monolayer. At a sufficient cluster size they merge and crystallize in the so-called low temperature phase with the contact plane {0 1 0} having a mosaicity of 1-2 . Furthermore, the observed crystallites show a distinct in-plane alignment, with a distribution of few degrees which perfectly explains the two needle directions. However, the molecules of the crystallites are slightly rotated to the oxygen rows, which is ascribed to a lattice match effect. Therefore it is concluded that the molecules of the monolayer are integrated in the crystal structure and undergo a slight realignment during 3D crystal growth. Finally the importance of an atomically ordered substrate surface is illustrated by a comparison to a film grown on an intentionally disordered surface leading to standing molecules without in-plane order. r
Sensor Letters, 2013
The Fe 2 O 3 and CoFe 2 O 4 nanoparticle-based Langmuir-Blodgett films for sensing of nitric diox... more The Fe 2 O 3 and CoFe 2 O 4 nanoparticle-based Langmuir-Blodgett films for sensing of nitric dioxide (NO 2 ) and acetone vapours have been explored. Both the sensitivity of the chemiresistors and dynamic properties, such as the response/recovery time, have been probed in dependence of the number of nanoparticle monolayers and working temperatures. The response of 23 at the NO 2 concentration of 1 ppm, i.e., approaching the canine detection limit, has been monitored implying the appropriateness for the detection of nitrate-based explosives. monolayers and thereby the controlled formation of the sensing film with targeted number of monolayers enabling to explore the effect of the film thickness on sensing properties.
Organic Electronics, 2007
The growth of sexithiophene ultra-thin films on an atomically clean Al(1 1 1) surface has been in... more The growth of sexithiophene ultra-thin films on an atomically clean Al(1 1 1) surface has been investigated by angleresolved ultraviolet photoemission spectroscopy. Although sexithiophene on Al(1 1 1) represents a weakly interacting system, sexithiophene molecules were found to dissociate even below room temperature, presumably via reactive sites. The mechanism is distinctly different to that claimed on the reverse system, i.e. aluminum evaporated on thiophene oligomers films, where isolated aluminum atoms were reported to covalently bond to thiophene rings and thus dramatically affect the molecule geometry and the conjugation. The effect of the insertion of an ultra-thin separator film of sexiphenyl, on the dissociation of sexithiophene was also examined.
Key Engineering Materials, 2014
The Fe2O3 and CoFe2O4 nanoparticle-based Langmuir-Blodgett lms for sensingof nitrogen dioxide (NO... more The Fe2O3 and CoFe2O4 nanoparticle-based Langmuir-Blodgett lms for sensingof nitrogen dioxide (NO2) and acetone vapours have been explored. Both the sensitivity of thechemiresistors and dynamic properties, such as the response/recovery time, have been probed independence of the number of nanoparticle monolayers and working temperatures. The responseof 23 at the NO2 concentration of 1 ppm has been monitored suggesting the pertinent sensitivityin the deep sub-ppm range, i.e. approaching the canine detection limit, and likewise implyingthe supposable detection of nitrate-based explosives.
Organic Electronics, 2007
The electronic level alignment of the organic semiconductor para-sexiphenyl on a nanoscopically p... more The electronic level alignment of the organic semiconductor para-sexiphenyl on a nanoscopically patterned substrate was investigated with ultraviolet photoemission spectroscopy, work function measurements and scanning tunnelling microscopy. The results show that for increasing coverage on inhomogeneous surfaces, shifts in electronic level alignment occur, which are due to the change from local to average band alignment. The Cu(1 1 0)-(2 · 1)O stripe phase, used as a model substrate consists of alternating stripes of bare and oxygen passivated copper, with stripe widths of $35 Å comparable to the sexiphenyl molecular length. In the first molecular layer the electronic bands are clearly aligned to the local surface potential of the specific stripe, resulting in the superposition of two photoemission spectra offset by 1 eV. Beyond two monolayers the valence band spectra clearly indicate a single electronic level alignment, which is determined by the average interface dipole.
Vacuum, 1998
This work reports on the X-ray photoemission spectroscopy (XPS) measurements of the As-rich GaAs(... more This work reports on the X-ray photoemission spectroscopy (XPS) measurements of the As-rich GaAs(001) surface properties developing due to the different thicknesses of the undoped silicon overlayers. We analyzed the bond nature on the silicon–GaAs interface depending on the silicon thickness which was connected with observed variations in surface Fermi level positions. Further, the Au\Si\n-GaAs metal-semiconductor contacts were prepared on
Thin Solid Films, 2012
ABSTRACT The electronic properties of molecular films are analysed with the consideration of the ... more ABSTRACT The electronic properties of molecular films are analysed with the consideration of the molecular orientation. The study demonstrates that surfaces of electroactive oligomeric molecular films can be classified—analogously to the elemental surfaces—by their intrinsic work functions. The intrinsic work function of molecular films is correlated with their ionisation energies; again, the behaviour is analogous to the correlation existing between the first ionisation energy of elements and the work function of the corresponding elemental surfaces. The proposed intrinsic work-function concept suggests that the mechanism for the energy-level alignment at the interfaces associated with molecular films is virtually controlled by work functions of materials brought into the contact.
Thin Solid Films, 2003
We present a study on electrical properties of AlySi N ySiyGaAs structure studied by deep level t... more We present a study on electrical properties of AlySi N ySiyGaAs structure studied by deep level transient spectroscopy and 3 4 capacitance-voltage technique. Here, the Si means an ultrathin silicon layer with thickness of approximately 2 nm. We have modelled the presented structure, while emissions from deep levels at SiyGaAs interface, traps in the bulk of GaAs and from a quantum well (QW) possibly formed by the Si interlayer, were taken into the account. Four deep traps were identified in the structure with the following thermal activation energies: 0.04, 0.19, 0.40 and 0.68 eV. The energy levels 0.4 and 0.68 are related with As defects, while the energy levels 0.04 and 0.19 are associated with the presence of the Si interlayer. Based on the emission behaviour, an existence of the QW is not probable (can be excluded). Rather, parameters of the Si-related energy levels suggest the levels are induced by d-doping of GaAs. ᮊ