Rodrigo Prioli - Academia.edu (original) (raw)

Papers by Rodrigo Prioli

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena, 2009

A combination of atomic force nanolithography and optical lithography, using amorphous arsenic su... more A combination of atomic force nanolithography and optical lithography, using amorphous arsenic sulfide as photoresist and a protective metallic layer mask, was used to fabricate metallic nanowires. It is shown that the scratch of the metallic mask can be performed without damage on the photoresist layer by a careful combination of the force applied by the microscope tip and a proper choice of the diamond tip scratching direction. The dimensions of the nanowires can be controlled by the depth and width of the scratched lines and the thickness of the deposited material used to grow the nanowires. The process has led to the deposition of continuous metallic nanowires with 200nm width and 25μm length.

Microscopy Research and Technique, 2021

In this work, the topographical effect of the scratching trajectory and the feed direction on the... more In this work, the topographical effect of the scratching trajectory and the feed direction on the formation of lithographed lines on the (001) InP surface was investigated using an atomic force microscope (AFM) tip‐based nanomachining approach. Nanoscratching tests were carried out using the sharp face of a diamond AFM tip in contact mode. From the topographic maps obtained by AFM, several morphological and fractal parameters were obtained and analyzed. Surface morphology presented a surface smoothing for surfaces with scratches produced in [011] and [001] directions. The height parameters confirmed this behavior because scratches in [001] direction exhibited lower roughness. Moreover, this scratch direction promoted the height distribution most symmetrical and platykurtic. The other morphological parameters revealed that this direction provided a more irregular surface (smaller Smc and Sxp), peak distribution, denser and pointed, smaller portion of material in the core, less deep f...

Scientific Reports, 2016

The nanoscale friction between an atomic force microscopy tip and graphene is investigated using ... more The nanoscale friction between an atomic force microscopy tip and graphene is investigated using friction force microscopy (FFM). During the tip movement, friction forces are observed to increase and then saturate in a highly anisotropic manner. As a result, the friction forces in graphene are highly dependent on the scanning direction: under some conditions, the energy dissipated along the armchair direction can be 80% higher than along the zigzag direction. In comparison, for highly-oriented pyrolitic graphite (HOPG), the friction anisotropy between armchair and zigzag directions is only 15%. This giant friction anisotropy in graphene results from anisotropies in the amplitudes of flexural deformations of the graphene sheet driven by the tip movement, not present in HOPG. The effect can be seen as a novel manifestation of the classical phenomenon of Euler buckling at the nanoscale, which provides the non-linear ingredients that amplify friction anisotropy. Simulations based on a n...

physica status solidi (a), 2001

The effects of nitrogen incorporation into amorphous boron carbide (B 4 C) films were studied. Th... more The effects of nitrogen incorporation into amorphous boron carbide (B 4 C) films were studied. The films were deposited by dc-magnetron sputtering with the Si substrates at room temperature. The nitrogen incorporation occurs at the expense of the boron content. The main feature of infrared absorption spectra obtained from B 4 C films is a broad band at around 1100 cm-1 that shifts to higher wavenumbers upon nitrogen incorporation. The spectra obtained from films with higher nitrogen content are typical of hexagonal boron nitride. The friction coefficient and the surface wear were studied by lateral force microscopy. The influence of several parameters like relative humidity, scanning velocity and load force was investigated. For boron-carbon nitride films, a weak dependence on the relative humidity of wear and friction coefficients was observed. In the case of B 4 C films, there is a clear correlation between the wear depth and the energy deposited at the AFM tip-film interface.

An investigation of the friction on the nanoscale was performed on amorphous carbon-fluorine film... more An investigation of the friction on the nanoscale was performed on amorphous carbon-fluorine films deposited by plasmaenhanced chemical vapor deposition. A direct correlation between friction forces, measured by lateral force microscopy in air, and the contact angles of the films was observed. The dependence of friction on the relative scanning velocity was also studied. The results show that the friction dependence on the velocity is influenced by the films' surface wettability. It is also shown that as the fluorine content in the films increases, there is an increase in the dependence of friction on the scanning velocity. These results highlight the influence of the capillary condensation of water between the moving parts on the nanoscale friction.

Ultramicroscopy, 2003

In this work, the lateral force profiles of the scanning force microscope tip on an amorphous sur... more In this work, the lateral force profiles of the scanning force microscope tip on an amorphous surface were simulated with the use of an independent oscillator model. The correlation between the lateral force profiles and the surface potential were studied as a function of the tip-surface normal force and relative scanning velocity. It is shown that the microscope resolution is governed by the quotient between the average potential interaction energy and the average elastic energy stored before the jumps. We show that there is an optimal velocity with which the scanning tip better senses the surface potential and we present its scaling laws.

Surface Review and Letters, 1999

Magnetic force microscopy (MFM) is used to investigate the surface magnetic structure of steels F... more Magnetic force microscopy (MFM) is used to investigate the surface magnetic structure of steels Fe–28Mn–8.5Al–1C–1.4Si under the different regimes of isothermal aging. A theoretical model for the MFM imaging of such structures is developed. Calculation of van der Waals forces is performed in order to interpret the topography images. The lateral resolution in terms of the magnetic field dependence on the surface coordinates is investigated. Finally, conditions that should be fulfilled for a good imaging of the samples are formulated.

physica status solidi (a), 2004

ABSTRACT When in ambient air, the contact between an atomic force microscope tip and a sample is ... more ABSTRACT When in ambient air, the contact between an atomic force microscope tip and a sample is usually wetted due to the capillary condensation of water. This water layer affects both the normal force at the nanoasperity contacts by the effect of a meniscus loading force and the friction force by the meniscus kinetics. In this work, the influence of the water condensation, at the tip surface contact, on the friction force is studied for hydrophilic, partially hydrophilic, and hydrophobic surfaces. It is shown that the surface wettability plays an important role on the dependence of friction with the normal force and scanning velocity. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Materials Science and Engineering: B, 2004

The nano-lithography of a metallic surface in air by atomic force microscopy while operated in co... more The nano-lithography of a metallic surface in air by atomic force microscopy while operated in contact mode and equipped with a diamond tip is presented. The aluminum mask was prepared by thermal deposition on arsenic sulfide films. The analysis of the scratches performed by the tip on the metallic mask show that the depth of the lithographed pattern increases with

Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 1996

Atomic force microscopy was used for the surface characterization of hard amorphous hydrogenated ... more Atomic force microscopy was used for the surface characterization of hard amorphous hydrogenated carbon–nitrogen films deposited by plasma enhanced chemical vapor deposition. The films were deposited onto silicon substrates by rf-plasma decomposition of methane–ammonia mixtures. The film roughness and the friction coefficient between the silicon nitride tip and the film surface were determined. The results indicate that the surface roughness increases with the amount of nitrogen incorporated in the film. The friction coefficients, measured in air, are almost constant for nitrogen incorporation up to 11 at. %.

Journal of Materials Science, 2008

The nanomechanical properties of polymethyl methacrylate and indium phosphide were measured with ... more The nanomechanical properties of polymethyl methacrylate and indium phosphide were measured with an atomic force microscope and a nanoindentation system. The elastic moduli measured with the atomic force microscope are in good agreement with the values obtained with the nanoindentation system. The hardness is shown to be affected by the tip radius used in our experiments. The cantilever vertical and lateral movements were independently analyzed during nanoindentation, and the tip torsion can be attributed to a change from elastic to plastic deformation regimes of materials during force microscopy nanoindentation. An analysis of the lateral movement of the laser beam associated with the cantilever torsion was used to determine the material yield stress.

Journal of Applied Physics, 2011

The direct determination of the crystallographic orientation of graphene sheets was performed usi... more The direct determination of the crystallographic orientation of graphene sheets was performed using lattice resolution atomic force microscopy images. A graphene sample, micromechanically exfoliated onto a SiO2 substrate showing well defined crystal edges, was imaged in lateral force mode. The lateral force images reveal the periodicity of the graphene hexagonal structure allowing the visualization of the lattice symmetries and determination of the crystal orientation. Crystal edges predominantly formed by zigzag or armchair directions were identified. The nature of the edges was confirmed by Raman spectroscopy.

Journal of Applied Physics, 2000

The investigation of the modifications of the nanoscale tribological properties of boron carbide ... more The investigation of the modifications of the nanoscale tribological properties of boron carbide films induced by the energy dissipation at the interface between the atomic force microscope tip and the film surface is presented. It is shown that the microscope tip induces a modification at the surface that results in a decrease on the friction forces between the tip and the film surface. The influences of the friction coefficient, the scanning speed, and the applied normal force on the film wear are investigated. Using a microscopic model, the dissipated energy at the tip–surface interface during scanning was estimated. The influence of the dissipated energy on the nanoscale wear is presented and a strong correlation between friction and wear, in nanoscale, is shown.

Journal of Applied Physics, 2012

Nanoindentations were performed on a cubic semiconductor using a cono-spherical diamond tip with ... more Nanoindentations were performed on a cubic semiconductor using a cono-spherical diamond tip with a 260 nm radius. The tip produces a single point of contact with the crystal surface allowing indentations with nano-scale dimensions. The early stages of deformation on (100) InP with the zinc-blende structure were observed to happen by the sequential introduction of metastable dislocation loops along the various slip planes directly beneath the point of contact. Locking of the dislocations loops forms a hardened region that acts as an extended tip during subsequent indentation, eventually leading to multiple bulk-like displacements (pop-in events) and to material pile up in the vicinity of the indentation pit. The first pop-in marks the transition of deformation from the nanometer to the micrometer scale.

Journal of Applied Physics, 2010

Linear arrays of InAs nanocrystals have been produced by metalorganic vapor phase epitaxy on scra... more Linear arrays of InAs nanocrystals have been produced by metalorganic vapor phase epitaxy on scratches performed with an atomic force microscope tip along specific crystallographic directions of an (100) InP wafer. Scratches along ⟨110⟩ generate highly mobile defects that extend far from the scratch region along easy-glide directions. On the other hand, ⟨100⟩ scratches result in highly-localized plastic deformation, hardening, and possibly frictional heating. In both cases, growth of nanocrystals was observed only on the scratched areas. Random nucleation of nanocrystals is observed along ⟨110⟩ scratches, while linearly ordered growth occur along ⟨100⟩ scratches. We attribute these observations to the delocalized nature of the dislocations in the ⟨110⟩ case, giving the appearance of random nucleation, while highly localized crystal defects along the ⟨100⟩ scratch lines act as nucleation sites for the growth of linear arrays of nanocrystals.

Journal of Applied Physics, 2011

The effect of scratch proximity on the resistance to plastic deformation in InP (100) crystals un... more The effect of scratch proximity on the resistance to plastic deformation in InP (100) crystals under low normal loads has been studied using atomic force microscopy (AFM) and transmission electron microscopy. Plastic flow has been observed for scratches performed with an atomic force microscope along ⟨110⟩ and ⟨100⟩ crystallographic directions. Plastic hardening has been determined from AFM measurements of the scratch depth and width, as a function of the distance between parallel scratches. For relatively low loads, hardening is found to be independent of the crystallographic direction of the scratch. Significant hardening takes place for scratch separations of less than ∼80 nm. Analysis of the microstructure indicates that hardening occurs due to the interaction of dislocations generated at adjacent scratches and acting on different slip planes.

Journal of Applied Physics, 2013

The microstructure of (001) InP crystals scratched with a sharp diamond tip depends strongly on t... more The microstructure of (001) InP crystals scratched with a sharp diamond tip depends strongly on the scratching direction. The scratch surface is found to conform to the radius of curvature of the tip (∼60 nm) by the formation of atomic crystal steps produced by dislocation glide along {111} planes. ⟨110⟩ scratches lead to coherent local crystal lattice movement and rotation causing deep dislocation propagation into the crystal and irregular pileups at the sides of the scratch surface. ⟨100⟩ scratches lead to incoherent lattice movement causing dislocation locking that inhibits their propagation and results in regular pileups.

Journal of Applied Physics, 2013

Nanoindentations were performed on various crystallographic orientations of single crystal ZnO us... more Nanoindentations were performed on various crystallographic orientations of single crystal ZnO using a cono-spherical diamond tip with a radius of curvature of 260 nm. The crystal orientations were the (112¯0) a-plane, (101¯0) m-plane, and (0001) c-plane (Zn-face). The optical properties associated with nanoindentation have been investigated by cathodoluminescence. The load-displacement curves show that the c-plane is the most resistive to deformation, followed by the m-plane, and the a-plane. A large number of non-radiative defects are created directly below the indentation, regardless of the crystal orientation. Nanoindentation on the a- and m-plane crystals activates slip along the (0001) basal planes, creating a band of non-radiative defects as well as tensile strain along the basal planes. Compressive strain is observed perpendicularly to the basal planes due to an absence of easy-glide mechanisms in these directions. The nanoindentation on the c-plane crystal results in region...

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena, 2009

A combination of atomic force nanolithography and optical lithography, using amorphous arsenic su... more A combination of atomic force nanolithography and optical lithography, using amorphous arsenic sulfide as photoresist and a protective metallic layer mask, was used to fabricate metallic nanowires. It is shown that the scratch of the metallic mask can be performed without damage on the photoresist layer by a careful combination of the force applied by the microscope tip and a proper choice of the diamond tip scratching direction. The dimensions of the nanowires can be controlled by the depth and width of the scratched lines and the thickness of the deposited material used to grow the nanowires. The process has led to the deposition of continuous metallic nanowires with 200nm width and 25μm length.

Microscopy Research and Technique, 2021

In this work, the topographical effect of the scratching trajectory and the feed direction on the... more In this work, the topographical effect of the scratching trajectory and the feed direction on the formation of lithographed lines on the (001) InP surface was investigated using an atomic force microscope (AFM) tip‐based nanomachining approach. Nanoscratching tests were carried out using the sharp face of a diamond AFM tip in contact mode. From the topographic maps obtained by AFM, several morphological and fractal parameters were obtained and analyzed. Surface morphology presented a surface smoothing for surfaces with scratches produced in [011] and [001] directions. The height parameters confirmed this behavior because scratches in [001] direction exhibited lower roughness. Moreover, this scratch direction promoted the height distribution most symmetrical and platykurtic. The other morphological parameters revealed that this direction provided a more irregular surface (smaller Smc and Sxp), peak distribution, denser and pointed, smaller portion of material in the core, less deep f...

Scientific Reports, 2016

The nanoscale friction between an atomic force microscopy tip and graphene is investigated using ... more The nanoscale friction between an atomic force microscopy tip and graphene is investigated using friction force microscopy (FFM). During the tip movement, friction forces are observed to increase and then saturate in a highly anisotropic manner. As a result, the friction forces in graphene are highly dependent on the scanning direction: under some conditions, the energy dissipated along the armchair direction can be 80% higher than along the zigzag direction. In comparison, for highly-oriented pyrolitic graphite (HOPG), the friction anisotropy between armchair and zigzag directions is only 15%. This giant friction anisotropy in graphene results from anisotropies in the amplitudes of flexural deformations of the graphene sheet driven by the tip movement, not present in HOPG. The effect can be seen as a novel manifestation of the classical phenomenon of Euler buckling at the nanoscale, which provides the non-linear ingredients that amplify friction anisotropy. Simulations based on a n...

physica status solidi (a), 2001

The effects of nitrogen incorporation into amorphous boron carbide (B 4 C) films were studied. Th... more The effects of nitrogen incorporation into amorphous boron carbide (B 4 C) films were studied. The films were deposited by dc-magnetron sputtering with the Si substrates at room temperature. The nitrogen incorporation occurs at the expense of the boron content. The main feature of infrared absorption spectra obtained from B 4 C films is a broad band at around 1100 cm-1 that shifts to higher wavenumbers upon nitrogen incorporation. The spectra obtained from films with higher nitrogen content are typical of hexagonal boron nitride. The friction coefficient and the surface wear were studied by lateral force microscopy. The influence of several parameters like relative humidity, scanning velocity and load force was investigated. For boron-carbon nitride films, a weak dependence on the relative humidity of wear and friction coefficients was observed. In the case of B 4 C films, there is a clear correlation between the wear depth and the energy deposited at the AFM tip-film interface.

An investigation of the friction on the nanoscale was performed on amorphous carbon-fluorine film... more An investigation of the friction on the nanoscale was performed on amorphous carbon-fluorine films deposited by plasmaenhanced chemical vapor deposition. A direct correlation between friction forces, measured by lateral force microscopy in air, and the contact angles of the films was observed. The dependence of friction on the relative scanning velocity was also studied. The results show that the friction dependence on the velocity is influenced by the films' surface wettability. It is also shown that as the fluorine content in the films increases, there is an increase in the dependence of friction on the scanning velocity. These results highlight the influence of the capillary condensation of water between the moving parts on the nanoscale friction.

Ultramicroscopy, 2003

In this work, the lateral force profiles of the scanning force microscope tip on an amorphous sur... more In this work, the lateral force profiles of the scanning force microscope tip on an amorphous surface were simulated with the use of an independent oscillator model. The correlation between the lateral force profiles and the surface potential were studied as a function of the tip-surface normal force and relative scanning velocity. It is shown that the microscope resolution is governed by the quotient between the average potential interaction energy and the average elastic energy stored before the jumps. We show that there is an optimal velocity with which the scanning tip better senses the surface potential and we present its scaling laws.

Surface Review and Letters, 1999

Magnetic force microscopy (MFM) is used to investigate the surface magnetic structure of steels F... more Magnetic force microscopy (MFM) is used to investigate the surface magnetic structure of steels Fe–28Mn–8.5Al–1C–1.4Si under the different regimes of isothermal aging. A theoretical model for the MFM imaging of such structures is developed. Calculation of van der Waals forces is performed in order to interpret the topography images. The lateral resolution in terms of the magnetic field dependence on the surface coordinates is investigated. Finally, conditions that should be fulfilled for a good imaging of the samples are formulated.

physica status solidi (a), 2004

ABSTRACT When in ambient air, the contact between an atomic force microscope tip and a sample is ... more ABSTRACT When in ambient air, the contact between an atomic force microscope tip and a sample is usually wetted due to the capillary condensation of water. This water layer affects both the normal force at the nanoasperity contacts by the effect of a meniscus loading force and the friction force by the meniscus kinetics. In this work, the influence of the water condensation, at the tip surface contact, on the friction force is studied for hydrophilic, partially hydrophilic, and hydrophobic surfaces. It is shown that the surface wettability plays an important role on the dependence of friction with the normal force and scanning velocity. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Materials Science and Engineering: B, 2004

The nano-lithography of a metallic surface in air by atomic force microscopy while operated in co... more The nano-lithography of a metallic surface in air by atomic force microscopy while operated in contact mode and equipped with a diamond tip is presented. The aluminum mask was prepared by thermal deposition on arsenic sulfide films. The analysis of the scratches performed by the tip on the metallic mask show that the depth of the lithographed pattern increases with

Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 1996

Atomic force microscopy was used for the surface characterization of hard amorphous hydrogenated ... more Atomic force microscopy was used for the surface characterization of hard amorphous hydrogenated carbon–nitrogen films deposited by plasma enhanced chemical vapor deposition. The films were deposited onto silicon substrates by rf-plasma decomposition of methane–ammonia mixtures. The film roughness and the friction coefficient between the silicon nitride tip and the film surface were determined. The results indicate that the surface roughness increases with the amount of nitrogen incorporated in the film. The friction coefficients, measured in air, are almost constant for nitrogen incorporation up to 11 at. %.

Journal of Materials Science, 2008

The nanomechanical properties of polymethyl methacrylate and indium phosphide were measured with ... more The nanomechanical properties of polymethyl methacrylate and indium phosphide were measured with an atomic force microscope and a nanoindentation system. The elastic moduli measured with the atomic force microscope are in good agreement with the values obtained with the nanoindentation system. The hardness is shown to be affected by the tip radius used in our experiments. The cantilever vertical and lateral movements were independently analyzed during nanoindentation, and the tip torsion can be attributed to a change from elastic to plastic deformation regimes of materials during force microscopy nanoindentation. An analysis of the lateral movement of the laser beam associated with the cantilever torsion was used to determine the material yield stress.

Journal of Applied Physics, 2011

The direct determination of the crystallographic orientation of graphene sheets was performed usi... more The direct determination of the crystallographic orientation of graphene sheets was performed using lattice resolution atomic force microscopy images. A graphene sample, micromechanically exfoliated onto a SiO2 substrate showing well defined crystal edges, was imaged in lateral force mode. The lateral force images reveal the periodicity of the graphene hexagonal structure allowing the visualization of the lattice symmetries and determination of the crystal orientation. Crystal edges predominantly formed by zigzag or armchair directions were identified. The nature of the edges was confirmed by Raman spectroscopy.

Journal of Applied Physics, 2000

The investigation of the modifications of the nanoscale tribological properties of boron carbide ... more The investigation of the modifications of the nanoscale tribological properties of boron carbide films induced by the energy dissipation at the interface between the atomic force microscope tip and the film surface is presented. It is shown that the microscope tip induces a modification at the surface that results in a decrease on the friction forces between the tip and the film surface. The influences of the friction coefficient, the scanning speed, and the applied normal force on the film wear are investigated. Using a microscopic model, the dissipated energy at the tip–surface interface during scanning was estimated. The influence of the dissipated energy on the nanoscale wear is presented and a strong correlation between friction and wear, in nanoscale, is shown.

Journal of Applied Physics, 2012

Nanoindentations were performed on a cubic semiconductor using a cono-spherical diamond tip with ... more Nanoindentations were performed on a cubic semiconductor using a cono-spherical diamond tip with a 260 nm radius. The tip produces a single point of contact with the crystal surface allowing indentations with nano-scale dimensions. The early stages of deformation on (100) InP with the zinc-blende structure were observed to happen by the sequential introduction of metastable dislocation loops along the various slip planes directly beneath the point of contact. Locking of the dislocations loops forms a hardened region that acts as an extended tip during subsequent indentation, eventually leading to multiple bulk-like displacements (pop-in events) and to material pile up in the vicinity of the indentation pit. The first pop-in marks the transition of deformation from the nanometer to the micrometer scale.

Journal of Applied Physics, 2010

Linear arrays of InAs nanocrystals have been produced by metalorganic vapor phase epitaxy on scra... more Linear arrays of InAs nanocrystals have been produced by metalorganic vapor phase epitaxy on scratches performed with an atomic force microscope tip along specific crystallographic directions of an (100) InP wafer. Scratches along ⟨110⟩ generate highly mobile defects that extend far from the scratch region along easy-glide directions. On the other hand, ⟨100⟩ scratches result in highly-localized plastic deformation, hardening, and possibly frictional heating. In both cases, growth of nanocrystals was observed only on the scratched areas. Random nucleation of nanocrystals is observed along ⟨110⟩ scratches, while linearly ordered growth occur along ⟨100⟩ scratches. We attribute these observations to the delocalized nature of the dislocations in the ⟨110⟩ case, giving the appearance of random nucleation, while highly localized crystal defects along the ⟨100⟩ scratch lines act as nucleation sites for the growth of linear arrays of nanocrystals.

Journal of Applied Physics, 2011

The effect of scratch proximity on the resistance to plastic deformation in InP (100) crystals un... more The effect of scratch proximity on the resistance to plastic deformation in InP (100) crystals under low normal loads has been studied using atomic force microscopy (AFM) and transmission electron microscopy. Plastic flow has been observed for scratches performed with an atomic force microscope along ⟨110⟩ and ⟨100⟩ crystallographic directions. Plastic hardening has been determined from AFM measurements of the scratch depth and width, as a function of the distance between parallel scratches. For relatively low loads, hardening is found to be independent of the crystallographic direction of the scratch. Significant hardening takes place for scratch separations of less than ∼80 nm. Analysis of the microstructure indicates that hardening occurs due to the interaction of dislocations generated at adjacent scratches and acting on different slip planes.

Journal of Applied Physics, 2013

The microstructure of (001) InP crystals scratched with a sharp diamond tip depends strongly on t... more The microstructure of (001) InP crystals scratched with a sharp diamond tip depends strongly on the scratching direction. The scratch surface is found to conform to the radius of curvature of the tip (∼60 nm) by the formation of atomic crystal steps produced by dislocation glide along {111} planes. ⟨110⟩ scratches lead to coherent local crystal lattice movement and rotation causing deep dislocation propagation into the crystal and irregular pileups at the sides of the scratch surface. ⟨100⟩ scratches lead to incoherent lattice movement causing dislocation locking that inhibits their propagation and results in regular pileups.

Journal of Applied Physics, 2013

Nanoindentations were performed on various crystallographic orientations of single crystal ZnO us... more Nanoindentations were performed on various crystallographic orientations of single crystal ZnO using a cono-spherical diamond tip with a radius of curvature of 260 nm. The crystal orientations were the (112¯0) a-plane, (101¯0) m-plane, and (0001) c-plane (Zn-face). The optical properties associated with nanoindentation have been investigated by cathodoluminescence. The load-displacement curves show that the c-plane is the most resistive to deformation, followed by the m-plane, and the a-plane. A large number of non-radiative defects are created directly below the indentation, regardless of the crystal orientation. Nanoindentation on the a- and m-plane crystals activates slip along the (0001) basal planes, creating a band of non-radiative defects as well as tensile strain along the basal planes. Compressive strain is observed perpendicularly to the basal planes due to an absence of easy-glide mechanisms in these directions. The nanoindentation on the c-plane crystal results in region...