Critical Reviews in Solid State and Materials Sciences, 2015
ABSTRACT Schottky and Ohmic contacts are essential parts of electronic and optoelectronic devices... more ABSTRACT Schottky and Ohmic contacts are essential parts of electronic and optoelectronic devices based on semiconductor materials. Controlling the contact/semiconductor interface properties is the key to obtain a contact with an optimum performance. Contacts incorporated by nanomaterials, i.e. nano-sized particles that are embedded at the interface of contact/semiconductor, can transform the conventional approaches of contact fabrication, resulting in more reproducible, tunable and efficient electronic and optoelectronic devices. This is a review of theoretical and fabrication progress on the last two decades to produce contacts with embedded nanoparticles (NPs). The review covers common routes of NPs deposition on different substrates (e.g. Si, Ge, SiC, GaN, GaAs, and InP) for nanostructured contact fabrication and the theoretical models to investigate the NPs effects on the conduction mechanism and electrical properties of devices.
Given the enormous importance of Au nanoparticles (NPs) deposition on Si substrates as the precur... more Given the enormous importance of Au nanoparticles (NPs) deposition on Si substrates as the precursor for various applications, we present an alternative approach to deposit Au NPs on linker-free n- and p-type Si substrates. It is demonstrated that, all conditions being similar, there is a significant difference between densities of the deposited NPs on both substrates. The Zeta-potential and polarity of charges surrounding the hydroxylamine reduced seeded growth Au NPs, are determined by a Zetasizer. To investigate the surface properties of Si substrates, contact angle measurement is performed. Field-emission scanning electron microscope is then utilized to distinguish the NPs density on the substrates. Finally, Al/Si Schottky barrier diodes with embedded Au NPs are fabricated, and their structural and electrical characteristics are further evaluated using an energy-filtered transmission electron microscope and current-voltage measurements, respectively. The results reveal that the density of NPs is significantly higher on n-type Si substrate and consequently has more pronounced effects on the electrical characteristics of the diode. It is concluded that protonation of Si-OH group on Si surface in low pH is responsible for the immobilization of Au NPs, which eventually contributes to the lowering of barrier height and enhances the electrical characteristics.
The microstructure of grain boundaries (GBs) in the commercial NdFeB-based alloy for permanent ma... more The microstructure of grain boundaries (GBs) in the commercial NdFeB-based alloy for permanent magnets has been studied. It is generally accepted that the unique hard magnetic properties of such alloys are controlled by the thin layers of a Nd-rich phase in Nd2Fe14B/Nd2Fe14B GBs. These GB layers ensure the magnetic isolation of Nd2Fe14B grains from each other. It is usually supposed that such GB layers contain metallic Nd or Nd-rich intermetallic compounds. However, the commercial NdFeB-based permanent magnets frequently contain a tangible amount of neodymium oxide Nd2O3 at the triple junctions between Nd2Fe14B grains. The goal of this work was to check whether the Nd2Fe14B/Nd2Fe14B GBs could also contain the thin layers of Nd2O3 oxide phase. Indeed, the screening with EELS-based elemental analysis permitted to observe that some of these Nd-rich layers in Nd2Fe14B/Nd2Fe14B GBs contain not only neodymium, but also oxygen. More detailed analysis of such GBs with high-resolution transmission electron microscopy (HR TEM) showed these GB layers are crystalline and have the lattice of neodymium oxide Nd2O3. In turn, the Lorentz micro-magnetic contrast in TEM permitted to observe that the Nd-oxide GB layers prevent the migration of domain walls from one Nd2Fe14B grain to another during remagnetization. This finding proves that the GB oxide layers, similar to those of metallic Nd or Nd-rich intermetallic compounds, can ensure the magnetic isolation between Nd2Fe14B grains needed for high coercivity. Therefore, the GB oxide layers can be used for further development of NdFeB-based permanent magnets.
36th International Electronics Manufacturing Technology Conference, 2014
ABSTRACT Modification of current density in back-to-back Schottky contacts without further heat t... more ABSTRACT Modification of current density in back-to-back Schottky contacts without further heat treatment processes is possible by embedding nanoparticles (NPs) into metal contacts with different work functions. In this work n-type Silicon (n-Si) back-to-back aluminum (Al) Schottky contacts embedded with gold (Au) NPs were fabricated using spin-coating technique. The effect of embedded NPs on the electrical properties were subsequently studied by current-voltage parameter analyzer. Effect of the density of Au NPs on Schottky barrier lowering and current density enhancement of the contacts were also studied and the energy band bending mechanism of Al/Si contacts with and without the NPs effect was proposed and discussed. The electrical results showed that by increasing the density of Au NPs spin-coated on Si, the current density in both bias directions has increased by more than two orders of magnitude. The increase in current density was attributed to the effect of NPs in electric field enhancement which subsequently resulted in Schottky barrier thinning and facilitation of field emission conduction and hence current density elevation.
ABSTRACT Nanostructured contacts, comprised of nanoparticles (NPs) embedded at the interface of c... more ABSTRACT Nanostructured contacts, comprised of nanoparticles (NPs) embedded at the interface of contact/ semiconductor, offer a viable solution in modification of Schottky barrier height (SBH) in Schottky contacts. The successful performance of devices with such nanostructured contacts requires a feasible selection of NPs/contact material based on theoretical calculations and a cost effective and reproducible route for NPs deposition. Acidification of commercially available colloidal Au NPs solution by HF has been selected here as a simple benchtop technique for deposition of Au NPs on n- and p-type 4H-SiC substrates. Theoretical calculations based on the model of inhomogeneity in SBH (ISBH) were used to make a more appropriate selection of NPs type (Au) and size (5 and 10 nm, diameter) with respect to contact metal (Al). Al/Au NPs/SiC Schottky barrier diodes were then fabricated, and their electrical characteristics exhibited current density enhancement due to the SBH lowering. The source of SBH lowering was determined to be the local electric field enhancement due to NPs effect, which was further investigated using the models of ISBH and tunneling enhancement at triple interface.
ABSTRACT Embedding metal nanoparticles (NPs) into metal contacts at metal–semiconductor (MS) inte... more ABSTRACT Embedding metal nanoparticles (NPs) into metal contacts at metal–semiconductor (MS) interface is an alternative method for modification of Schottky barrier height (SBH) and compared with traditional methods that might result in an undesired alteration of the MS interface, offers a tremendous simplification and adaptation in processing steps. There is a direct link between the type, size and density of NPs and their interaction with contact/semiconductor and the improved electrical characteristics. A comprehensive analysis of the NPs effect at MS interface is required to make appropriate and efficient selection of contact/NPs combination as well as deposition of NPs and fabrication of nanostructured contact. In this work, multiple successive depositions of colloidal Au NPs by spin-coating are used as an alternative and simple method to deposit Au NPs on n- and p-Si substrates. Electrical parameters of Au NPs/Al nanostructured contacts including SBH and ideality factor are in turn extracted from current–voltage characteristics. Two models of inhomogeneity in SBH and enhanced tunneling at triple interface are then invoked for further analysis of the NPs effect on electrical properties of contacts. The best model proposed to describe this phenomenology is the enhanced tunneling at triple interface.
Colloidal gold (Au) nanoparticles (NPs) deposition on silicon (Si) substrate is highly affected b... more Colloidal gold (Au) nanoparticles (NPs) deposition on silicon (Si) substrate is highly affected by the deposition technique and surface properties of the substrate. Spin-coating technique has been proven to be an efficient approach in terms of cost, time and maintaining the quality of the deposition. However, to prevent the agglomeration of NPs and obtain desirable density and distribution of NPs on the substrate, precise control of the spin-coating parameters is required. In this study colloidal Au NPs were spin-coated onto a modified, yet linker-free Si surface. By controlling the spinning speed, acceleration, dwelling time, and the volume of NPs colloidal solution, the density and distribution of the NPs on Si were optimized. Scanning electron microscope was used to investigate the NPs density in each step of the process. Results showed that the distribution of NPs on Si substrate is highly dependent on the spinning speed, duration, and acceleration rate as well as surface proper...
We introduce a facile approach to transfer thin films and other mechanically sensitive TEM sample... more We introduce a facile approach to transfer thin films and other mechanically sensitive TEM samples inside a FIB with minimal introduction of stress and bending. The method is making use of a pre-synthetized flexible free-standing Ag nanowire attached to the tip of a typical tungsten micromanipulator inside the FIB. The main advantages of this approach are the significantly reduced stress-induced bending during transfer and attachment of the TEM sample, the very short time required to attach and cut the nanowire, the operation at very low dose and ion current, and only using the e-beam for Pt deposition during the transfer of sensitive TEM samples. This results in a reduced sample preparation time and reduced exposure to the ion beam or e-beam for Pt deposition during the sample preparation and thus also reduced contamination and beam damage. The method was applied to a number of thin films and different TEM samples in order to illustrate the advantageous benefits of the concept. In particular, the technique has been successfully tested for the transfer of a thin film onto a MEMS heating chip for in situ TEM experiments.
Critical Reviews in Solid State and Materials Sciences
Schottky and Ohmic contacts are essential parts of electronic and optoelectronic devices based ... more Schottky and Ohmic contacts are essential parts of electronic and optoelectronic devices based on semiconductor materials. Controlling the contact/semiconductor interface properties is the key to obtaining a contact with an optimum performance. Contacts incorporated by nanomaterials, i.e., nano-sized particles that are embedded at the interface of contact/semiconductor, can transform the conventional approaches of contact fabrication, resulting in more reproducible, tunable and efficient electronic, and optoelectronic devices. This article is a review of theoretical and fabrication progress on the last two decades to produce contacts with embedded nanoparticles (NPs). The review covers common routes of NPs deposition on different substrates (e.g., Si, Ge, SiC, GaN, GaAs67P33, and InP) for nanostructured contact fabrication and the theoretical models to investigate the NPs effects on the conduction mechanism and electrical properties of devices.
Given the enormous importance of Au nanoparticles (NPs) deposition on Si substrates as the precur... more Given the enormous importance of Au nanoparticles (NPs) deposition on Si substrates as the precursor for various applications, we present an alternative approach to deposit Au NPs on linker-free n- and p-type Si substrates. It is demonstrated that, all conditions being similar, there is a significant difference between densities of the deposited NPs on both substrates. The Zeta-potential and polarity of charges surrounding the hydroxylamine reduced seeded growth Au NPs, are determined by a Zetasizer. To investigate the surface properties of Si substrates, contact angle measurement is performed. Field-emission scanning electron microscope is then utilized to distinguish the NPs density on the substrates. Finally, Al/Si Schottky barrier diodes with embedded Au NPs are fabricated, and their structural and electrical characteristics are further evaluated using an energy-filtered transmission electron microscope and current–voltage measurements, respectively. The results reveal that the density of NPs is significantly higher on n-type Si substrate and consequently has more pronounced effects on the electrical characteristics of the diode. It is concluded that protonation of Si–OH group on Si surface in low pH is responsible for the immobilization of Au NPs, which eventually contributes to the lowering of barrier height and enhances the electrical characteristics.
Critical Reviews in Solid State and Materials Sciences, 2015
ABSTRACT Schottky and Ohmic contacts are essential parts of electronic and optoelectronic devices... more ABSTRACT Schottky and Ohmic contacts are essential parts of electronic and optoelectronic devices based on semiconductor materials. Controlling the contact/semiconductor interface properties is the key to obtain a contact with an optimum performance. Contacts incorporated by nanomaterials, i.e. nano-sized particles that are embedded at the interface of contact/semiconductor, can transform the conventional approaches of contact fabrication, resulting in more reproducible, tunable and efficient electronic and optoelectronic devices. This is a review of theoretical and fabrication progress on the last two decades to produce contacts with embedded nanoparticles (NPs). The review covers common routes of NPs deposition on different substrates (e.g. Si, Ge, SiC, GaN, GaAs, and InP) for nanostructured contact fabrication and the theoretical models to investigate the NPs effects on the conduction mechanism and electrical properties of devices.
Given the enormous importance of Au nanoparticles (NPs) deposition on Si substrates as the precur... more Given the enormous importance of Au nanoparticles (NPs) deposition on Si substrates as the precursor for various applications, we present an alternative approach to deposit Au NPs on linker-free n- and p-type Si substrates. It is demonstrated that, all conditions being similar, there is a significant difference between densities of the deposited NPs on both substrates. The Zeta-potential and polarity of charges surrounding the hydroxylamine reduced seeded growth Au NPs, are determined by a Zetasizer. To investigate the surface properties of Si substrates, contact angle measurement is performed. Field-emission scanning electron microscope is then utilized to distinguish the NPs density on the substrates. Finally, Al/Si Schottky barrier diodes with embedded Au NPs are fabricated, and their structural and electrical characteristics are further evaluated using an energy-filtered transmission electron microscope and current-voltage measurements, respectively. The results reveal that the density of NPs is significantly higher on n-type Si substrate and consequently has more pronounced effects on the electrical characteristics of the diode. It is concluded that protonation of Si-OH group on Si surface in low pH is responsible for the immobilization of Au NPs, which eventually contributes to the lowering of barrier height and enhances the electrical characteristics.
The microstructure of grain boundaries (GBs) in the commercial NdFeB-based alloy for permanent ma... more The microstructure of grain boundaries (GBs) in the commercial NdFeB-based alloy for permanent magnets has been studied. It is generally accepted that the unique hard magnetic properties of such alloys are controlled by the thin layers of a Nd-rich phase in Nd2Fe14B/Nd2Fe14B GBs. These GB layers ensure the magnetic isolation of Nd2Fe14B grains from each other. It is usually supposed that such GB layers contain metallic Nd or Nd-rich intermetallic compounds. However, the commercial NdFeB-based permanent magnets frequently contain a tangible amount of neodymium oxide Nd2O3 at the triple junctions between Nd2Fe14B grains. The goal of this work was to check whether the Nd2Fe14B/Nd2Fe14B GBs could also contain the thin layers of Nd2O3 oxide phase. Indeed, the screening with EELS-based elemental analysis permitted to observe that some of these Nd-rich layers in Nd2Fe14B/Nd2Fe14B GBs contain not only neodymium, but also oxygen. More detailed analysis of such GBs with high-resolution transmission electron microscopy (HR TEM) showed these GB layers are crystalline and have the lattice of neodymium oxide Nd2O3. In turn, the Lorentz micro-magnetic contrast in TEM permitted to observe that the Nd-oxide GB layers prevent the migration of domain walls from one Nd2Fe14B grain to another during remagnetization. This finding proves that the GB oxide layers, similar to those of metallic Nd or Nd-rich intermetallic compounds, can ensure the magnetic isolation between Nd2Fe14B grains needed for high coercivity. Therefore, the GB oxide layers can be used for further development of NdFeB-based permanent magnets.
36th International Electronics Manufacturing Technology Conference, 2014
ABSTRACT Modification of current density in back-to-back Schottky contacts without further heat t... more ABSTRACT Modification of current density in back-to-back Schottky contacts without further heat treatment processes is possible by embedding nanoparticles (NPs) into metal contacts with different work functions. In this work n-type Silicon (n-Si) back-to-back aluminum (Al) Schottky contacts embedded with gold (Au) NPs were fabricated using spin-coating technique. The effect of embedded NPs on the electrical properties were subsequently studied by current-voltage parameter analyzer. Effect of the density of Au NPs on Schottky barrier lowering and current density enhancement of the contacts were also studied and the energy band bending mechanism of Al/Si contacts with and without the NPs effect was proposed and discussed. The electrical results showed that by increasing the density of Au NPs spin-coated on Si, the current density in both bias directions has increased by more than two orders of magnitude. The increase in current density was attributed to the effect of NPs in electric field enhancement which subsequently resulted in Schottky barrier thinning and facilitation of field emission conduction and hence current density elevation.
ABSTRACT Nanostructured contacts, comprised of nanoparticles (NPs) embedded at the interface of c... more ABSTRACT Nanostructured contacts, comprised of nanoparticles (NPs) embedded at the interface of contact/ semiconductor, offer a viable solution in modification of Schottky barrier height (SBH) in Schottky contacts. The successful performance of devices with such nanostructured contacts requires a feasible selection of NPs/contact material based on theoretical calculations and a cost effective and reproducible route for NPs deposition. Acidification of commercially available colloidal Au NPs solution by HF has been selected here as a simple benchtop technique for deposition of Au NPs on n- and p-type 4H-SiC substrates. Theoretical calculations based on the model of inhomogeneity in SBH (ISBH) were used to make a more appropriate selection of NPs type (Au) and size (5 and 10 nm, diameter) with respect to contact metal (Al). Al/Au NPs/SiC Schottky barrier diodes were then fabricated, and their electrical characteristics exhibited current density enhancement due to the SBH lowering. The source of SBH lowering was determined to be the local electric field enhancement due to NPs effect, which was further investigated using the models of ISBH and tunneling enhancement at triple interface.
ABSTRACT Embedding metal nanoparticles (NPs) into metal contacts at metal–semiconductor (MS) inte... more ABSTRACT Embedding metal nanoparticles (NPs) into metal contacts at metal–semiconductor (MS) interface is an alternative method for modification of Schottky barrier height (SBH) and compared with traditional methods that might result in an undesired alteration of the MS interface, offers a tremendous simplification and adaptation in processing steps. There is a direct link between the type, size and density of NPs and their interaction with contact/semiconductor and the improved electrical characteristics. A comprehensive analysis of the NPs effect at MS interface is required to make appropriate and efficient selection of contact/NPs combination as well as deposition of NPs and fabrication of nanostructured contact. In this work, multiple successive depositions of colloidal Au NPs by spin-coating are used as an alternative and simple method to deposit Au NPs on n- and p-Si substrates. Electrical parameters of Au NPs/Al nanostructured contacts including SBH and ideality factor are in turn extracted from current–voltage characteristics. Two models of inhomogeneity in SBH and enhanced tunneling at triple interface are then invoked for further analysis of the NPs effect on electrical properties of contacts. The best model proposed to describe this phenomenology is the enhanced tunneling at triple interface.
Colloidal gold (Au) nanoparticles (NPs) deposition on silicon (Si) substrate is highly affected b... more Colloidal gold (Au) nanoparticles (NPs) deposition on silicon (Si) substrate is highly affected by the deposition technique and surface properties of the substrate. Spin-coating technique has been proven to be an efficient approach in terms of cost, time and maintaining the quality of the deposition. However, to prevent the agglomeration of NPs and obtain desirable density and distribution of NPs on the substrate, precise control of the spin-coating parameters is required. In this study colloidal Au NPs were spin-coated onto a modified, yet linker-free Si surface. By controlling the spinning speed, acceleration, dwelling time, and the volume of NPs colloidal solution, the density and distribution of the NPs on Si were optimized. Scanning electron microscope was used to investigate the NPs density in each step of the process. Results showed that the distribution of NPs on Si substrate is highly dependent on the spinning speed, duration, and acceleration rate as well as surface proper...
We introduce a facile approach to transfer thin films and other mechanically sensitive TEM sample... more We introduce a facile approach to transfer thin films and other mechanically sensitive TEM samples inside a FIB with minimal introduction of stress and bending. The method is making use of a pre-synthetized flexible free-standing Ag nanowire attached to the tip of a typical tungsten micromanipulator inside the FIB. The main advantages of this approach are the significantly reduced stress-induced bending during transfer and attachment of the TEM sample, the very short time required to attach and cut the nanowire, the operation at very low dose and ion current, and only using the e-beam for Pt deposition during the transfer of sensitive TEM samples. This results in a reduced sample preparation time and reduced exposure to the ion beam or e-beam for Pt deposition during the sample preparation and thus also reduced contamination and beam damage. The method was applied to a number of thin films and different TEM samples in order to illustrate the advantageous benefits of the concept. In particular, the technique has been successfully tested for the transfer of a thin film onto a MEMS heating chip for in situ TEM experiments.
Critical Reviews in Solid State and Materials Sciences
Schottky and Ohmic contacts are essential parts of electronic and optoelectronic devices based ... more Schottky and Ohmic contacts are essential parts of electronic and optoelectronic devices based on semiconductor materials. Controlling the contact/semiconductor interface properties is the key to obtaining a contact with an optimum performance. Contacts incorporated by nanomaterials, i.e., nano-sized particles that are embedded at the interface of contact/semiconductor, can transform the conventional approaches of contact fabrication, resulting in more reproducible, tunable and efficient electronic, and optoelectronic devices. This article is a review of theoretical and fabrication progress on the last two decades to produce contacts with embedded nanoparticles (NPs). The review covers common routes of NPs deposition on different substrates (e.g., Si, Ge, SiC, GaN, GaAs67P33, and InP) for nanostructured contact fabrication and the theoretical models to investigate the NPs effects on the conduction mechanism and electrical properties of devices.
Given the enormous importance of Au nanoparticles (NPs) deposition on Si substrates as the precur... more Given the enormous importance of Au nanoparticles (NPs) deposition on Si substrates as the precursor for various applications, we present an alternative approach to deposit Au NPs on linker-free n- and p-type Si substrates. It is demonstrated that, all conditions being similar, there is a significant difference between densities of the deposited NPs on both substrates. The Zeta-potential and polarity of charges surrounding the hydroxylamine reduced seeded growth Au NPs, are determined by a Zetasizer. To investigate the surface properties of Si substrates, contact angle measurement is performed. Field-emission scanning electron microscope is then utilized to distinguish the NPs density on the substrates. Finally, Al/Si Schottky barrier diodes with embedded Au NPs are fabricated, and their structural and electrical characteristics are further evaluated using an energy-filtered transmission electron microscope and current–voltage measurements, respectively. The results reveal that the density of NPs is significantly higher on n-type Si substrate and consequently has more pronounced effects on the electrical characteristics of the diode. It is concluded that protonation of Si–OH group on Si surface in low pH is responsible for the immobilization of Au NPs, which eventually contributes to the lowering of barrier height and enhances the electrical characteristics.
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Papers by Saleh Gorji
been studied. It is generally accepted that the unique hard magnetic properties of such alloys are controlled by
the thin layers of a Nd-rich phase in Nd2Fe14B/Nd2Fe14B GBs. These GB layers ensure the magnetic isolation of
Nd2Fe14B grains from each other. It is usually supposed that such GB layers contain metallic Nd or Nd-rich intermetallic
compounds. However, the commercial NdFeB-based permanent magnets frequently contain a tangible
amount of neodymium oxide Nd2O3 at the triple junctions between Nd2Fe14B grains. The goal of this work was
to check whether the Nd2Fe14B/Nd2Fe14B GBs could also contain the thin layers of Nd2O3 oxide phase. Indeed,
the screening with EELS-based elemental analysis permitted to observe that some of these Nd-rich layers in
Nd2Fe14B/Nd2Fe14B GBs contain not only neodymium, but also oxygen. More detailed analysis of such GBs
with high-resolution transmission electron microscopy (HR TEM) showed these GB layers are crystalline and
have the lattice of neodymium oxide Nd2O3. In turn, the Lorentz micro-magnetic contrast in TEM permitted to
observe that the Nd-oxide GB layers prevent the migration of domain walls from one Nd2Fe14B grain to another
during remagnetization. This finding proves that the GB oxide layers, similar to those of metallic Nd or Nd-rich
intermetallic compounds, can ensure the magnetic isolation between Nd2Fe14B grains needed for high coercivity.
Therefore, the GB oxide layers can be used for further development of NdFeB-based permanent magnets.
been studied. It is generally accepted that the unique hard magnetic properties of such alloys are controlled by
the thin layers of a Nd-rich phase in Nd2Fe14B/Nd2Fe14B GBs. These GB layers ensure the magnetic isolation of
Nd2Fe14B grains from each other. It is usually supposed that such GB layers contain metallic Nd or Nd-rich intermetallic
compounds. However, the commercial NdFeB-based permanent magnets frequently contain a tangible
amount of neodymium oxide Nd2O3 at the triple junctions between Nd2Fe14B grains. The goal of this work was
to check whether the Nd2Fe14B/Nd2Fe14B GBs could also contain the thin layers of Nd2O3 oxide phase. Indeed,
the screening with EELS-based elemental analysis permitted to observe that some of these Nd-rich layers in
Nd2Fe14B/Nd2Fe14B GBs contain not only neodymium, but also oxygen. More detailed analysis of such GBs
with high-resolution transmission electron microscopy (HR TEM) showed these GB layers are crystalline and
have the lattice of neodymium oxide Nd2O3. In turn, the Lorentz micro-magnetic contrast in TEM permitted to
observe that the Nd-oxide GB layers prevent the migration of domain walls from one Nd2Fe14B grain to another
during remagnetization. This finding proves that the GB oxide layers, similar to those of metallic Nd or Nd-rich
intermetallic compounds, can ensure the magnetic isolation between Nd2Fe14B grains needed for high coercivity.
Therefore, the GB oxide layers can be used for further development of NdFeB-based permanent magnets.