Peter Hutár - Academia.edu (original) (raw)
Papers by Peter Hutár
Inorganic chemistry, Jul 1, 2024
Applied physics letters, Mar 18, 2024
Zenodo (CERN European Organization for Nuclear Research), Sep 3, 2023
Journal of Physical Chemistry C, Aug 6, 2020
The crystallographic alignment of an ultra-thin MoS 2 film strongly influences its properties and... more The crystallographic alignment of an ultra-thin MoS 2 film strongly influences its properties and is, therefore, substantial for various applications. Developing the methods for controlled growth is of primary importance for a reproducible film fabrication. Among them, sulfurization of pre-deposited molybdenum or molybdenum oxide films is a method capable of growing large-area MoS 2 layers with reasonable control over the layer alignment. However, the question of which growth parameters define the layer alignment remains still unresolved. We prepared 10 nm thick films of Mo and Mo oxides with different degrees of crystallinity and sulfurized them all at the same conditions. We demonstrate that the presence of the crystalline phase of MoO 2 or MoO 3 in the parent films promotes the growth of the horizontally aligned MoS 2. This observation provides a simple criterion for controlling the layer alignment and for the growth of horizontal MoS 2 layers of thickness at which only the vertical layers have hitherto been assumed to grow.
NANOCOM ..., 2022
Nowadays, 2D materials are one of the most studied classes of materials. In addition to the most ... more Nowadays, 2D materials are one of the most studied classes of materials. In addition to the most famous graphene, progress has been achieved in studying and using fundamental properties of transition metal dichalcogenides (TMD). Complementary, diamond as a representative of 3D materials has gained a reputation as an extremely versatile material due to its extraordinary combination of physical/chemical/electrical/optical properties. Besides these particular forms of 2D and 3D materials, their heterostructures have become very attractive due to new phenomena and functions (bandgap engineering, enhanced charge transport, optical interaction, etc.). However, individual technological procedures are still minimally investigated and described. Here, we will demonstrate a proof-of-concept for the preparation of MoS2/diamond heterostructures, where two different strategies were employed: a) growth of MoS2 layers on diamond films, and b) growth of diamond films on Si/MoS2 substrates. Considering the growth conditions for MoS2 and diamond materials, heterostructures based on MoS2 on diamond can be prepared more easily. Regardless of the diamond film's morphology, the grown MoS2 layer simply copies the diamond surface and does not damage the diamond film. However, the heterostructure in the configuration of diamond on MoS2 is a highly challenging task. It was found experimentally that the combination of deposition temperature and aggressive chemical-plasma environment during diamond growth places high demands on the resistance and stability of MoS2 layers.
Inorganic Chemistry, Oct 25, 2022
physica status solidi (b), 2019
Two-dimensional transition metal dichalcogenides (TMD) attract high research interest due to thei... more Two-dimensional transition metal dichalcogenides (TMD) attract high research interest due to their electronic properties and MoS 2 is likely the most explored compound of this group. We report on the fabrication of MoS 2 thin films by sulfurization of pre-deposited MoO 3 layers on a c-plane sapphire substrate by RF magnetron sputtering from stoichiometric MoO 3 target. The structure and properties of as-grown MoO 3 and MoS 2 layers were characterized by several methods including x-ray diffraction, grazing-incidence wide-angle X-ray scattering, photoelectron spectroscopy, Raman spectroscopy, and AFM. Furthermore, we studied the influence of the crystallographic structure of MoO 3 layers on the final MoS 2 films. We focused on the influence of the crystallographic structure of MoO 3 on the resulting MoS 2 films. A strong texturation in the c-axis direction and an indication of a high degree of inplane orientation of MoS 2 thin films on the c-sapphire substrate was observed. 1.Introduction MoS 2 belongs to the most studied 2D TMD materials due to its electronic and optoelectronic properties. A monolayer of MoS 2 is a semiconductor with a direct band gap of 1.9 eV [1]. The enhancement of photo-luminescent intensity and the direct band gap within the energy range of visible light are attractive for future optoelectronic devices [2]. The fundamental properties of MoS 2 have been studied on mechanically exfoliated flakes or chemical vapor deposited (CVD) triangle-shaped layers [3,4]. Sulfurization of thin molybdenum or molybdenum oxide layers is a simple and cost-effective method to synthesize MoS 2 thin films on a wafer scale. The synthesis is carried out directly on the pre-deposited precursor films. Sulfurization takes place in sulfur vapors, H 2 S/Ar gas or H 2 S/Ar gas plasma [5]. The electronic, structural, optical and transport properties of fabricated MoS 2 films can be controlled by sulfurization
The Journal of Physical Chemistry C, 2021
Some of the distinct optical, catalytical, and electronic properties of few-layer MoS 2 films ari... more Some of the distinct optical, catalytical, and electronic properties of few-layer MoS 2 films arise from a specific orientation of the MoS 2 layers. The growth of horizontally or vertically aligned MoS 2 during the sulfurization of predeposited Mo film can be controlled by various physical conditions such as temperature, heating rate, Mo film thickness, or sulfur vapor pressure. However, due to the inherent limitations of performing real-time and in situ experiments during sulfurization in a standard growth chamber, only a limited number of analytical techniques can be used to elucidate the in-process phase transformation. Here, we present a comprehensive real-time study of the growth of few-layer MoS 2 films by sulfurization of Mo films using in situ grazing-incidence wide-angle X-ray scattering. We demonstrate that the process gas flow, and thus the sulfur partial vapor pressure, is the key control parameter for the few-layer MoS 2 layer orientation while all other process parameters remain fixed. Tracking the crystallization of few-layer MoS 2 layers in real-time allowed us to estimate the activation energy required for both horizontal and vertical orientations. Growth of either horizontal or vertical MoS 2 was observed without a metastable transition between them throughout the sulfurization.
Applied Surface Science, 2021
Abstract The frictional properties of two-dimensional (2D) materials are strongly dependent on th... more Abstract The frictional properties of two-dimensional (2D) materials are strongly dependent on the crystallographic orientation and number of layers. Although friction anisotropy caused by crystallographic orientations has been reported for various 2D materials, the flexural deformations and different defects complicate the insight into the mechanism of the in-plane friction anisotropy of these materials. Here, the anisotropic friction behavior between an atomic force microscopy tip and monolayer (ML) and few-layer (FL) MoSe2 flakes grown by CVD was performed by nanofriction measurements at different crystallographic directions, applied loads (FA), and tip scanning velocities. Our results reveal that the angular dependence of the friction forces is highly anisotropic for both types of MoSe2 flakes, and the anisotropy decreases with FA. Importantly, the anisotropies demonstrate opposite angular dependence for ML and FL MoSe2 flakes. As confirmed by the friction scanning velocity dependences, this difference seems to originate from different friction mechanisms for ML and FL MoSe2 flakes. The friction of FL flakes was predominantly influenced by atomic stick–slip motion. In contrast, ML MoSe2 is characterized by a coexistence of deformation-induced and atomic stick–slip motion. The experimental results presented here extend the understanding of the tribological properties of dry lubricants operating at the nanoscale.
Applied Surface Science, 2021
Abstract In recent years, molybdenum disulfide (MoS2) has been investigated due to its unique ele... more Abstract In recent years, molybdenum disulfide (MoS2) has been investigated due to its unique electronic, optical, and mechanical properties with a variety of applications. Sulfurization of pre-deposited MoO3 layers is one of the methods of the preparation of large-area MoS2 thin films. The MoO3 layers have been grown on c-sapphire substrates, using two different techniques (rf sputtering, pulsed laser deposition). The films were subsequently annealed in vapors of sulfur at high temperatures what converted them to MoS2 films. The quality of MoS2 is strongly influenced by the properties of the precursor MoO3 layers. The pre-deposited MoO3, as well as the sulfurized MoS2, have been characterized by several techniques including Raman, Rutherford backscattering spectroscopy, atomic force microscopy, scanning electron microscopy, and X-ray diffraction. Here we compare two types of MoS2 films prepared from different MoO3 layers to determine the most suitable MoO3 layer properties providing good quality MoS2 films for future applications.
Sulfurization of a Mo layer is one of the most used methods for preparation of thin MoS2 films. I... more Sulfurization of a Mo layer is one of the most used methods for preparation of thin MoS2 films. In the method, a sulfur powder and Mo covered substrate are placed in different positions within a furnace, and heated separately. This requires a furnace having at least two zones. Here, we present a simplified version of the method where a one-zone tube furnace was used. A molybdenum film on a substrate and a sulfur powder were placed in the center of the furnace and heated at temperatures above 800°C. Mo films transform into MoS2 in vapors of sulphur at high temperatures. As-prepared films were characterized by number of techniques including X-ray diffraction (XRD), atomic force microscopy (AFM), transmission electron microscopy (TEM), Raman, Rutherford backscattering (RBS) and X-ray photoelectron spectroscopy (XPS). It appears that one-zone sulfurization, with just one annealing temperature used, is a suitable method for fabrication of MoS2 thin films. This method is fast, cheap and e...
The crystallographic alignment of an ultra-thin MoS2 film strongly influences its properties and ... more The crystallographic alignment of an ultra-thin MoS2 film strongly influences its properties and is, therefore, substantial for various applications. Developing the methods for controlled growth is...
ACS Omega
Thin films of transition-metal dichalcogenides are potential materials for optoelectronic applica... more Thin films of transition-metal dichalcogenides are potential materials for optoelectronic applications. However, the application of these materials in practice requires knowledge of their fundamental optical properties. Many existing methods determine optical constants using predefined models. Here, a different approach was used. We determine the sheet conductance and absorption coefficient of few-layer PtSe 2 in the infrared and UV−vis ranges without recourse to any particular model for the optical constants. PtSe 2 samples with a thickness of about 3−4 layers were prepared by selenization of 0.5 nm thick platinum films on sapphire substrates at different temperatures. Differential reflectance was extracted from transmittance and reflectance measurements from the front and back of the sample. The film thickness, limited to a few atomic layers, allowed a thin-film approximation to calculate the optical conductance and absorption coefficient. The former has a very different energy dependence in the infrared, near-infrared, and visible ranges. The absorption coefficient exhibits a strong power-law dependence on energy with an exponent larger than three in the mid-infrared and nearinfrared regions. We have not observed any evidence for a band gap in PtSe 2 thin layers down to an energy of 0.4 eV from our optical measurements.
Physical chemistry chemical physics : PCCP, 2020
Small π-conjugated organic molecules have attracted substantial attention in the past decade as t... more Small π-conjugated organic molecules have attracted substantial attention in the past decade as they are considered as candidates for future organic-based (opto-)electronic applications. The molecular arrangement in the organic layer is one of the crucial parameters that determine the efficiency of a given device. The desired orientation of the molecules is achieved by a proper choice of the underlying substrate and growth conditions. Typically, one underlying material supports only one inherent molecular orientation at its interface. Here, we report on two different orientations of diindenoperylene (DIP) molecules on the same underlayer, i.e. on a few-layer MoS2 substrate. We show that DIP molecules adopt a lying-down orientation when deposited on few-layer MoS2 with horizontally oriented layers. In contrast, for vertically aligned MoS2 layers, DIP molecules are arranged in a standing-up manner. Employing in situ and real-time grazing-incidence wide-angle X-ray scattering (GIWAXS),...
Schematic representation of the GIWAXS measurements on HA and VA MoS2 layers.
Ongoing interest in two-dimensional (2D) layered materials has motivated extensive studies of tra... more Ongoing interest in two-dimensional (2D) layered materials has motivated extensive studies of transitional metal dichalcogenides, especially its most pronounced representative, MoS2. The few-layer MoS2 exhibits distinct properties from those in bulk, which predetermine its potential usage in optoelectronics and flexible devices. Recently, it was found that the layer orientation in MoS2 thin films is a key parameter for their utilization in specific devices. Thus far, the alignment of MoS2 layers has been detected mostly by transmission electron microscopy (TEM). The drawback of this method is that it requires elaborate sample preparation and probes only a nanometer-scale area of the sample surface. Here we present polarized Raman spectroscopy which provides information about the MoS2 layer orientation on the area a few orders larger than in TEM. We show that the depolarization ratio of the significant Raman peaks A1g and E2g show specific values for the vertical and horizontal align...
Inorganic chemistry, Jul 1, 2024
Applied physics letters, Mar 18, 2024
Zenodo (CERN European Organization for Nuclear Research), Sep 3, 2023
Journal of Physical Chemistry C, Aug 6, 2020
The crystallographic alignment of an ultra-thin MoS 2 film strongly influences its properties and... more The crystallographic alignment of an ultra-thin MoS 2 film strongly influences its properties and is, therefore, substantial for various applications. Developing the methods for controlled growth is of primary importance for a reproducible film fabrication. Among them, sulfurization of pre-deposited molybdenum or molybdenum oxide films is a method capable of growing large-area MoS 2 layers with reasonable control over the layer alignment. However, the question of which growth parameters define the layer alignment remains still unresolved. We prepared 10 nm thick films of Mo and Mo oxides with different degrees of crystallinity and sulfurized them all at the same conditions. We demonstrate that the presence of the crystalline phase of MoO 2 or MoO 3 in the parent films promotes the growth of the horizontally aligned MoS 2. This observation provides a simple criterion for controlling the layer alignment and for the growth of horizontal MoS 2 layers of thickness at which only the vertical layers have hitherto been assumed to grow.
NANOCOM ..., 2022
Nowadays, 2D materials are one of the most studied classes of materials. In addition to the most ... more Nowadays, 2D materials are one of the most studied classes of materials. In addition to the most famous graphene, progress has been achieved in studying and using fundamental properties of transition metal dichalcogenides (TMD). Complementary, diamond as a representative of 3D materials has gained a reputation as an extremely versatile material due to its extraordinary combination of physical/chemical/electrical/optical properties. Besides these particular forms of 2D and 3D materials, their heterostructures have become very attractive due to new phenomena and functions (bandgap engineering, enhanced charge transport, optical interaction, etc.). However, individual technological procedures are still minimally investigated and described. Here, we will demonstrate a proof-of-concept for the preparation of MoS2/diamond heterostructures, where two different strategies were employed: a) growth of MoS2 layers on diamond films, and b) growth of diamond films on Si/MoS2 substrates. Considering the growth conditions for MoS2 and diamond materials, heterostructures based on MoS2 on diamond can be prepared more easily. Regardless of the diamond film's morphology, the grown MoS2 layer simply copies the diamond surface and does not damage the diamond film. However, the heterostructure in the configuration of diamond on MoS2 is a highly challenging task. It was found experimentally that the combination of deposition temperature and aggressive chemical-plasma environment during diamond growth places high demands on the resistance and stability of MoS2 layers.
Inorganic Chemistry, Oct 25, 2022
physica status solidi (b), 2019
Two-dimensional transition metal dichalcogenides (TMD) attract high research interest due to thei... more Two-dimensional transition metal dichalcogenides (TMD) attract high research interest due to their electronic properties and MoS 2 is likely the most explored compound of this group. We report on the fabrication of MoS 2 thin films by sulfurization of pre-deposited MoO 3 layers on a c-plane sapphire substrate by RF magnetron sputtering from stoichiometric MoO 3 target. The structure and properties of as-grown MoO 3 and MoS 2 layers were characterized by several methods including x-ray diffraction, grazing-incidence wide-angle X-ray scattering, photoelectron spectroscopy, Raman spectroscopy, and AFM. Furthermore, we studied the influence of the crystallographic structure of MoO 3 layers on the final MoS 2 films. We focused on the influence of the crystallographic structure of MoO 3 on the resulting MoS 2 films. A strong texturation in the c-axis direction and an indication of a high degree of inplane orientation of MoS 2 thin films on the c-sapphire substrate was observed. 1.Introduction MoS 2 belongs to the most studied 2D TMD materials due to its electronic and optoelectronic properties. A monolayer of MoS 2 is a semiconductor with a direct band gap of 1.9 eV [1]. The enhancement of photo-luminescent intensity and the direct band gap within the energy range of visible light are attractive for future optoelectronic devices [2]. The fundamental properties of MoS 2 have been studied on mechanically exfoliated flakes or chemical vapor deposited (CVD) triangle-shaped layers [3,4]. Sulfurization of thin molybdenum or molybdenum oxide layers is a simple and cost-effective method to synthesize MoS 2 thin films on a wafer scale. The synthesis is carried out directly on the pre-deposited precursor films. Sulfurization takes place in sulfur vapors, H 2 S/Ar gas or H 2 S/Ar gas plasma [5]. The electronic, structural, optical and transport properties of fabricated MoS 2 films can be controlled by sulfurization
The Journal of Physical Chemistry C, 2021
Some of the distinct optical, catalytical, and electronic properties of few-layer MoS 2 films ari... more Some of the distinct optical, catalytical, and electronic properties of few-layer MoS 2 films arise from a specific orientation of the MoS 2 layers. The growth of horizontally or vertically aligned MoS 2 during the sulfurization of predeposited Mo film can be controlled by various physical conditions such as temperature, heating rate, Mo film thickness, or sulfur vapor pressure. However, due to the inherent limitations of performing real-time and in situ experiments during sulfurization in a standard growth chamber, only a limited number of analytical techniques can be used to elucidate the in-process phase transformation. Here, we present a comprehensive real-time study of the growth of few-layer MoS 2 films by sulfurization of Mo films using in situ grazing-incidence wide-angle X-ray scattering. We demonstrate that the process gas flow, and thus the sulfur partial vapor pressure, is the key control parameter for the few-layer MoS 2 layer orientation while all other process parameters remain fixed. Tracking the crystallization of few-layer MoS 2 layers in real-time allowed us to estimate the activation energy required for both horizontal and vertical orientations. Growth of either horizontal or vertical MoS 2 was observed without a metastable transition between them throughout the sulfurization.
Applied Surface Science, 2021
Abstract The frictional properties of two-dimensional (2D) materials are strongly dependent on th... more Abstract The frictional properties of two-dimensional (2D) materials are strongly dependent on the crystallographic orientation and number of layers. Although friction anisotropy caused by crystallographic orientations has been reported for various 2D materials, the flexural deformations and different defects complicate the insight into the mechanism of the in-plane friction anisotropy of these materials. Here, the anisotropic friction behavior between an atomic force microscopy tip and monolayer (ML) and few-layer (FL) MoSe2 flakes grown by CVD was performed by nanofriction measurements at different crystallographic directions, applied loads (FA), and tip scanning velocities. Our results reveal that the angular dependence of the friction forces is highly anisotropic for both types of MoSe2 flakes, and the anisotropy decreases with FA. Importantly, the anisotropies demonstrate opposite angular dependence for ML and FL MoSe2 flakes. As confirmed by the friction scanning velocity dependences, this difference seems to originate from different friction mechanisms for ML and FL MoSe2 flakes. The friction of FL flakes was predominantly influenced by atomic stick–slip motion. In contrast, ML MoSe2 is characterized by a coexistence of deformation-induced and atomic stick–slip motion. The experimental results presented here extend the understanding of the tribological properties of dry lubricants operating at the nanoscale.
Applied Surface Science, 2021
Abstract In recent years, molybdenum disulfide (MoS2) has been investigated due to its unique ele... more Abstract In recent years, molybdenum disulfide (MoS2) has been investigated due to its unique electronic, optical, and mechanical properties with a variety of applications. Sulfurization of pre-deposited MoO3 layers is one of the methods of the preparation of large-area MoS2 thin films. The MoO3 layers have been grown on c-sapphire substrates, using two different techniques (rf sputtering, pulsed laser deposition). The films were subsequently annealed in vapors of sulfur at high temperatures what converted them to MoS2 films. The quality of MoS2 is strongly influenced by the properties of the precursor MoO3 layers. The pre-deposited MoO3, as well as the sulfurized MoS2, have been characterized by several techniques including Raman, Rutherford backscattering spectroscopy, atomic force microscopy, scanning electron microscopy, and X-ray diffraction. Here we compare two types of MoS2 films prepared from different MoO3 layers to determine the most suitable MoO3 layer properties providing good quality MoS2 films for future applications.
Sulfurization of a Mo layer is one of the most used methods for preparation of thin MoS2 films. I... more Sulfurization of a Mo layer is one of the most used methods for preparation of thin MoS2 films. In the method, a sulfur powder and Mo covered substrate are placed in different positions within a furnace, and heated separately. This requires a furnace having at least two zones. Here, we present a simplified version of the method where a one-zone tube furnace was used. A molybdenum film on a substrate and a sulfur powder were placed in the center of the furnace and heated at temperatures above 800°C. Mo films transform into MoS2 in vapors of sulphur at high temperatures. As-prepared films were characterized by number of techniques including X-ray diffraction (XRD), atomic force microscopy (AFM), transmission electron microscopy (TEM), Raman, Rutherford backscattering (RBS) and X-ray photoelectron spectroscopy (XPS). It appears that one-zone sulfurization, with just one annealing temperature used, is a suitable method for fabrication of MoS2 thin films. This method is fast, cheap and e...
The crystallographic alignment of an ultra-thin MoS2 film strongly influences its properties and ... more The crystallographic alignment of an ultra-thin MoS2 film strongly influences its properties and is, therefore, substantial for various applications. Developing the methods for controlled growth is...
ACS Omega
Thin films of transition-metal dichalcogenides are potential materials for optoelectronic applica... more Thin films of transition-metal dichalcogenides are potential materials for optoelectronic applications. However, the application of these materials in practice requires knowledge of their fundamental optical properties. Many existing methods determine optical constants using predefined models. Here, a different approach was used. We determine the sheet conductance and absorption coefficient of few-layer PtSe 2 in the infrared and UV−vis ranges without recourse to any particular model for the optical constants. PtSe 2 samples with a thickness of about 3−4 layers were prepared by selenization of 0.5 nm thick platinum films on sapphire substrates at different temperatures. Differential reflectance was extracted from transmittance and reflectance measurements from the front and back of the sample. The film thickness, limited to a few atomic layers, allowed a thin-film approximation to calculate the optical conductance and absorption coefficient. The former has a very different energy dependence in the infrared, near-infrared, and visible ranges. The absorption coefficient exhibits a strong power-law dependence on energy with an exponent larger than three in the mid-infrared and nearinfrared regions. We have not observed any evidence for a band gap in PtSe 2 thin layers down to an energy of 0.4 eV from our optical measurements.
Physical chemistry chemical physics : PCCP, 2020
Small π-conjugated organic molecules have attracted substantial attention in the past decade as t... more Small π-conjugated organic molecules have attracted substantial attention in the past decade as they are considered as candidates for future organic-based (opto-)electronic applications. The molecular arrangement in the organic layer is one of the crucial parameters that determine the efficiency of a given device. The desired orientation of the molecules is achieved by a proper choice of the underlying substrate and growth conditions. Typically, one underlying material supports only one inherent molecular orientation at its interface. Here, we report on two different orientations of diindenoperylene (DIP) molecules on the same underlayer, i.e. on a few-layer MoS2 substrate. We show that DIP molecules adopt a lying-down orientation when deposited on few-layer MoS2 with horizontally oriented layers. In contrast, for vertically aligned MoS2 layers, DIP molecules are arranged in a standing-up manner. Employing in situ and real-time grazing-incidence wide-angle X-ray scattering (GIWAXS),...
Schematic representation of the GIWAXS measurements on HA and VA MoS2 layers.
Ongoing interest in two-dimensional (2D) layered materials has motivated extensive studies of tra... more Ongoing interest in two-dimensional (2D) layered materials has motivated extensive studies of transitional metal dichalcogenides, especially its most pronounced representative, MoS2. The few-layer MoS2 exhibits distinct properties from those in bulk, which predetermine its potential usage in optoelectronics and flexible devices. Recently, it was found that the layer orientation in MoS2 thin films is a key parameter for their utilization in specific devices. Thus far, the alignment of MoS2 layers has been detected mostly by transmission electron microscopy (TEM). The drawback of this method is that it requires elaborate sample preparation and probes only a nanometer-scale area of the sample surface. Here we present polarized Raman spectroscopy which provides information about the MoS2 layer orientation on the area a few orders larger than in TEM. We show that the depolarization ratio of the significant Raman peaks A1g and E2g show specific values for the vertical and horizontal align...