Roberto Machorro | UNAM - Academia.edu (original) (raw)
Papers by Roberto Machorro
Applied Optics, 1978
Bedford, Mass. 01730, and should be accompanied by a signed Copyright Transfer Agreement. If auth... more Bedford, Mass. 01730, and should be accompanied by a signed Copyright Transfer Agreement. If authors will state in their covering communications whether they expect their institutions to pay the publication charge, publication time should be shortened (for those who do).
Applied Optics, 1991
In a glass-metal-dielectric system, it is normally impossible to determine simultaneously the com... more In a glass-metal-dielectric system, it is normally impossible to determine simultaneously the complex dielectric constant, the thickness of the metal, and the corresponding parameters of a dielectric overlayer. We propose the use of the pseudo-Brewster or Abeles angle as an additional parameter to characterize simultaneously a dielectric thin-film overcoating and the metal surface parameters. We use a Kretschmann attenuated-total-reflection configuration. An admittance diagram is used to illustrate graphically the role of an absentee layer at this angle. A study of the limitations of the method is also presented.
… Journal of Modern …, 2009
A set of AlN thin films was prepared by reactive magnetron sputtering at room temperature. The ef... more A set of AlN thin films was prepared by reactive magnetron sputtering at room temperature. The effect of oxygen impurities on the structural and optical properties of AlN films is discussed. The structural and optical properties were characterized using X-ray diffraction (XRD) and ...
Catalysis Today, 2005
Small copper clusters Cu n feasible in zeolites (in the range of sizes 5 < n < 9) were simulated ... more Small copper clusters Cu n feasible in zeolites (in the range of sizes 5 < n < 9) were simulated with ab initio quantum chemical calculations, and results were compared with the experimental data on optical absorption of copper-exchanged and reduced zeolites. The short-wavelength absorption features in the spectra of Cu-mordenite, Cu-zeolite-beta, and Cu-ZSM-5 are interpreted as stabilization of fewatomic copper clusters with nuclearity in the range n = 6-8 according to the geometrical factor, while in the range with l > 500 nm the familiar plasmon resonance band due to copper nanoparticles was observed. A comparison of the data for the three types of zeolites with theoretical results can argue on the occurrence of the clusters stabilized within channels under mild reduction conditions. The most probable candidates to fit the cavities of mordenite, zeolite-beta and ZSM-5 are positively charged clusters Cu 6 + , Cu 7 + and Cu 8 + with point groups C 2v (2), D 5h and C 2v (1), respectively.
Diamond and Related Materials, 2006
Silicon Carbide thin films have been prepared by RF reactive magnetron sputtering of a silicon ta... more Silicon Carbide thin films have been prepared by RF reactive magnetron sputtering of a silicon target in a mixture of Ar and CH4. Surface analysis was performed by X-ray photoelectron spectroscopy (XPS) to examine the elemental bonding at the surface and in bulk of the material. Optical analysis was carried out by ellipsometry to study the optical constants (n and
Applied Optics, 2006
We present an alternative method for cutting optical glass. It works with a high-pressure fluid, ... more We present an alternative method for cutting optical glass. It works with a high-pressure fluid, carring abrasive powder. This technique offers some advantages over conventional methods that use diamond abrasive covered wires or disks. We make a critical comparison between those two techniques, characterizing cuts with interferometric, polarimetric, and Ronchi testing. The main feature of the water-jet technique is that it allows surface of any shape, already polished, to be cut safely.
Journal of Vacuum Science & Technology A, 2005
The desire to merge the most advantageous physical and chemical properties of both SiO2 and Si3N4... more The desire to merge the most advantageous physical and chemical properties of both SiO2 and Si3N4 in an optimum combination tailored to various applications in electrical, optical, and optoelectronic thin films has pushed a continuous interest in the processing of SiOxNy thin films. Inhomogeneous thin film filters have had an increasing importance in the industry as optical filters. Silicon oxynitride, SiOxNy, is a very interesting material for multiple applications, including graded refractive index films. The refractive index can be changed from pure silicon dioxide (1.47) to silicon nitride (2.4) by just varying the film composition. We report the growth of SiOxNy films by reactive laser ablation using two different solid targets, Si3N4 and Si, in the ambient of N2 and O2 at various pressures, introduced separately in the growth chamber, as the film is monitored by real time ellipsometry. The oxidation rate in the films is studied for both targets. The composition of the films is in situ determined by Auger-electron spectroscopy and x-ray photoemission spectroscopy. The evolution of the chemical bonding of the species in the film is done by Fourier transform infrared. The SiOxNy film stoichiometry, bonding character, and optical properties are compared as a function of O2 pressure while N2 pressure is maintained fixed as either the Si3N4 or Si target is ablated.
Applied Surface Science, 2003
Tungsten nitride (WN x ) films were grown on silicon and glass slide substrates by laser ablating... more Tungsten nitride (WN x ) films were grown on silicon and glass slide substrates by laser ablating a tungsten target in molecular nitrogen ambient. By in situ Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and electron energy loss spectroscopy (EELS), the films density, elemental composition and chemical state were determined. Ex situ, the films were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Also, the transmittance and resistivity of the film on glass substrates were determined. The results show that the reaction of tungsten and nitrogen is effective; the nitrogen is integrated in the tungsten matrix changing gradually the electronic configuration, chemical states and film properties. Since with this preparation method the obtained films are of high quality, low resistivity and dense, this makes attractive to growth tungsten nitride films for technological applications. #
Applied Surface Science, 1998
SiN overlayers have been grown on quartz and single-crystal Si substrates at room temperature by ... more SiN overlayers have been grown on quartz and single-crystal Si substrates at room temperature by ablating a Si N x 3 4 sintered target in a vacuum environment and different gas atmospheres, N and Ar. The film growth was controlled by real 2 time ellipsometry at a fixed photon-energy, 2.5 eV. Once the deposition process is completed, in situ spectro-ellipsometric measurements were obtained in the 1.5 to 5 eV photon-energy range. The best curve fitting of the data is used to find the film composition: a mixture of non-crystalline Si N , polycrystalline Si, p-Si, and amorphous Si, a-Si. The film crystallinity 3 4
Thin Solid Films, 2003
Beryllium nitride thin films, which are candidates for optoelectronic applications, have been gro... more Beryllium nitride thin films, which are candidates for optoelectronic applications, have been grown by pulsed laser deposition on silicon substrates. The films were prepared by ablating a beryllium foil in N environment at several pressures and substrate 2 temperatures. Real-time ellipsometric monitoring for the period of deposition were carried out by a multiwavelength ellipsometer in the 1.625(hn(4.405 eV photon-energy range. After its completion, the films were characterized in situ by electron spectroscopies and ex situ by atomic force and scanning electron microcopies. A model for the growth of beryllium nitride was applied to reproduce the optical measurement and concurrently, the refractive index from the visible to the near ultraviolet spectral region was calculated. The estimated optical bandgap correlates closely with previously published theoretical results. ᮊ
Applied Surface Science, 2003
Tungsten oxide thin films have been prepared by reactive pulsed laser deposition (PLD). Substrate... more Tungsten oxide thin films have been prepared by reactive pulsed laser deposition (PLD). Substrate heat treatment and oxygen partial pressure during growth are correlated with Auger electron (AES), X-ray photoelectron (XPS), electron energy loss (EELS) and ...
Diamond and Related Materials, 2003
A set of aluminium nitride (AlN), thin films were prepared by DC-reactive magnetron sputtering. T... more A set of aluminium nitride (AlN), thin films were prepared by DC-reactive magnetron sputtering. The deposition parameters, such as substrate temperature, sputtering gas composition and plasma current were varied. Spectroscopic ellipsometry, XPS, RBS, XRD, SEM, AFM and FTIR techniques were utilized to study the relationship between film properties and preparation conditions. We observed that the optical and surface properties have a strong dependence on the deposition rate. All prepared films present a composition close to AlN stoichiometry, even for nitrogen to argon gas concentrations below 1:2. The near surface of AlN films exposed to atmosphere was primarily composed of Al O while the bulk was AlN with some minor contamination of 2 3 oxygen and carbon. The thickness of the oxide layer was reduced when higher plasma current and lower nitrogen concentration were used. Deposits prepared at 400 8C presented the best refractive index and deposition rate, for both utilized plasma currents. ᮊ
Applied Surface Science, 2001
A series of samples were prepared by reactive laser ablation of a graphite target in nitrogen env... more A series of samples were prepared by reactive laser ablation of a graphite target in nitrogen environment. The CN x ®lms were annealed from room temperature to 900 8C, and in situ analyzed by electron energy loss spectroscopy (EELS), Auger electron spectroscopy, X-ray photoelectron spectroscopy and temperature desorption spectroscopy (TDS). A [N]/[C] ratio of 0.43 was determined and decreases notoriously as the annealing temperature increases. The peak shapes and intensities in the N 1s and C 1s regions are similar to those reported by other research groups. Small satellite peaks were observed in the N 1s and C 1s regions, corresponding to ®rst-and second-order inelastic energy losses of the main peaks. These losses were detected also by EELS with an energy of 4 eV and assigned to the p±p à plasmon. This resonance is distinctive of non-localized electrons in an sp 2 -hybridized carbon orbital. Thereafter, the main N 1s and C 1s peaks could be assigned to atoms in a six-and ®ve-member rings. Moreover, the ®lms were easily degraded by the thermal treatment and the main desorption product determined by TDS was found to be C 2 N 2 . We concluded that the most probable structure is one where N atoms dope graphite-like carbon layers by substitution, causing three-dimensional polymerization reactions, with chemical states similar to Upilex, Kapton and other polyimides. #
Solid State Communications, 1997
A process for obtaining Sro.3_3y/zLa,Bao,7Nbz06 (LSBN) ceramics at different concentrations of th... more A process for obtaining Sro.3_3y/zLa,Bao,7Nbz06 (LSBN) ceramics at different concentrations of the La3+ cation and different sintering times is presented. The dielectric properties of the LSBN system where Sr2+ ions are substituted by La3+ cations follow the pattern of a modification by cationic substitution for a constant Sr/Ba ratio. This behavior of the dielectric properties indicate that the La3+ cations occupy the A1 as well as the A2 sites which favors the formation of the LSBN system up to y c 0.05. For higher values the dielectric properties of the ceramic start to deteriorate. Copyright 0 1997 Published by Elsevier Science Ltd
Materials Letters, 2002
Beryllium nitride thin films were grown on silicon substrates by laser ablating a beryllium foil ... more Beryllium nitride thin films were grown on silicon substrates by laser ablating a beryllium foil in molecular nitrogen ambient. The composition and chemical state were determined with Auger (AES), X-Ray photoelectron (XPS) and energy loss (EELS) spectroscopies. A low absorption coefficient in the visible region, and an optical bandgap of 3.8 eV, determined by reflectance ellipsometry, were obtained for films grown at nitrogen pressures higher than 25 mTorr. The results show that the reaction of beryllium with nitrogen is very effective using this preparation method, producing high quality films.
Materials Letters, 2000
x y 3 4
Applied Surface Science, 1998
. In this work, thin films of SiCN have been deposited by pulsed laser deposition on silicon subs... more . In this work, thin films of SiCN have been deposited by pulsed laser deposition on silicon substrates by KrF 248 nm excimer laser ablation of a SiC sintered target in a vacuum system at room temperature. To obtain various stoichiometries, molecular nitrogen is introduced in the deposition chamber in the 5 to 500 mTorr pressure range. The resultant SiC N films
Applied Optics, 1990
Amorphous selenium films were produced by vacuum evaporation onto glass and aluminum substrates. ... more Amorphous selenium films were produced by vacuum evaporation onto glass and aluminum substrates. The chemical composition of the films and interfaces were studied using scanning Auger electron spectroscopy.
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 1997
Work is described on the fabrication of uncoated probe tips for reflection scanning near-field op... more Work is described on the fabrication of uncoated probe tips for reflection scanning near-field optical microscopes. A chemical etching process with a rotator, and a simple device to make the tips by a heating-pulling method without a heating laser are introduced. Both ...
Ferroelectrics, 1999
Abstract Pt thin films were deposited on Ti/Glass and TiO2/Si substrates by DC sputtering at temp... more Abstract Pt thin films were deposited on Ti/Glass and TiO2/Si substrates by DC sputtering at temperatures between room and 700° C to optimize its performance as electrodes for ferroelectric devices. Well oriented films in the (111) direction were obtained. Auger ...
Applied Optics, 1978
Bedford, Mass. 01730, and should be accompanied by a signed Copyright Transfer Agreement. If auth... more Bedford, Mass. 01730, and should be accompanied by a signed Copyright Transfer Agreement. If authors will state in their covering communications whether they expect their institutions to pay the publication charge, publication time should be shortened (for those who do).
Applied Optics, 1991
In a glass-metal-dielectric system, it is normally impossible to determine simultaneously the com... more In a glass-metal-dielectric system, it is normally impossible to determine simultaneously the complex dielectric constant, the thickness of the metal, and the corresponding parameters of a dielectric overlayer. We propose the use of the pseudo-Brewster or Abeles angle as an additional parameter to characterize simultaneously a dielectric thin-film overcoating and the metal surface parameters. We use a Kretschmann attenuated-total-reflection configuration. An admittance diagram is used to illustrate graphically the role of an absentee layer at this angle. A study of the limitations of the method is also presented.
… Journal of Modern …, 2009
A set of AlN thin films was prepared by reactive magnetron sputtering at room temperature. The ef... more A set of AlN thin films was prepared by reactive magnetron sputtering at room temperature. The effect of oxygen impurities on the structural and optical properties of AlN films is discussed. The structural and optical properties were characterized using X-ray diffraction (XRD) and ...
Catalysis Today, 2005
Small copper clusters Cu n feasible in zeolites (in the range of sizes 5 < n < 9) were simulated ... more Small copper clusters Cu n feasible in zeolites (in the range of sizes 5 < n < 9) were simulated with ab initio quantum chemical calculations, and results were compared with the experimental data on optical absorption of copper-exchanged and reduced zeolites. The short-wavelength absorption features in the spectra of Cu-mordenite, Cu-zeolite-beta, and Cu-ZSM-5 are interpreted as stabilization of fewatomic copper clusters with nuclearity in the range n = 6-8 according to the geometrical factor, while in the range with l > 500 nm the familiar plasmon resonance band due to copper nanoparticles was observed. A comparison of the data for the three types of zeolites with theoretical results can argue on the occurrence of the clusters stabilized within channels under mild reduction conditions. The most probable candidates to fit the cavities of mordenite, zeolite-beta and ZSM-5 are positively charged clusters Cu 6 + , Cu 7 + and Cu 8 + with point groups C 2v (2), D 5h and C 2v (1), respectively.
Diamond and Related Materials, 2006
Silicon Carbide thin films have been prepared by RF reactive magnetron sputtering of a silicon ta... more Silicon Carbide thin films have been prepared by RF reactive magnetron sputtering of a silicon target in a mixture of Ar and CH4. Surface analysis was performed by X-ray photoelectron spectroscopy (XPS) to examine the elemental bonding at the surface and in bulk of the material. Optical analysis was carried out by ellipsometry to study the optical constants (n and
Applied Optics, 2006
We present an alternative method for cutting optical glass. It works with a high-pressure fluid, ... more We present an alternative method for cutting optical glass. It works with a high-pressure fluid, carring abrasive powder. This technique offers some advantages over conventional methods that use diamond abrasive covered wires or disks. We make a critical comparison between those two techniques, characterizing cuts with interferometric, polarimetric, and Ronchi testing. The main feature of the water-jet technique is that it allows surface of any shape, already polished, to be cut safely.
Journal of Vacuum Science & Technology A, 2005
The desire to merge the most advantageous physical and chemical properties of both SiO2 and Si3N4... more The desire to merge the most advantageous physical and chemical properties of both SiO2 and Si3N4 in an optimum combination tailored to various applications in electrical, optical, and optoelectronic thin films has pushed a continuous interest in the processing of SiOxNy thin films. Inhomogeneous thin film filters have had an increasing importance in the industry as optical filters. Silicon oxynitride, SiOxNy, is a very interesting material for multiple applications, including graded refractive index films. The refractive index can be changed from pure silicon dioxide (1.47) to silicon nitride (2.4) by just varying the film composition. We report the growth of SiOxNy films by reactive laser ablation using two different solid targets, Si3N4 and Si, in the ambient of N2 and O2 at various pressures, introduced separately in the growth chamber, as the film is monitored by real time ellipsometry. The oxidation rate in the films is studied for both targets. The composition of the films is in situ determined by Auger-electron spectroscopy and x-ray photoemission spectroscopy. The evolution of the chemical bonding of the species in the film is done by Fourier transform infrared. The SiOxNy film stoichiometry, bonding character, and optical properties are compared as a function of O2 pressure while N2 pressure is maintained fixed as either the Si3N4 or Si target is ablated.
Applied Surface Science, 2003
Tungsten nitride (WN x ) films were grown on silicon and glass slide substrates by laser ablating... more Tungsten nitride (WN x ) films were grown on silicon and glass slide substrates by laser ablating a tungsten target in molecular nitrogen ambient. By in situ Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and electron energy loss spectroscopy (EELS), the films density, elemental composition and chemical state were determined. Ex situ, the films were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Also, the transmittance and resistivity of the film on glass substrates were determined. The results show that the reaction of tungsten and nitrogen is effective; the nitrogen is integrated in the tungsten matrix changing gradually the electronic configuration, chemical states and film properties. Since with this preparation method the obtained films are of high quality, low resistivity and dense, this makes attractive to growth tungsten nitride films for technological applications. #
Applied Surface Science, 1998
SiN overlayers have been grown on quartz and single-crystal Si substrates at room temperature by ... more SiN overlayers have been grown on quartz and single-crystal Si substrates at room temperature by ablating a Si N x 3 4 sintered target in a vacuum environment and different gas atmospheres, N and Ar. The film growth was controlled by real 2 time ellipsometry at a fixed photon-energy, 2.5 eV. Once the deposition process is completed, in situ spectro-ellipsometric measurements were obtained in the 1.5 to 5 eV photon-energy range. The best curve fitting of the data is used to find the film composition: a mixture of non-crystalline Si N , polycrystalline Si, p-Si, and amorphous Si, a-Si. The film crystallinity 3 4
Thin Solid Films, 2003
Beryllium nitride thin films, which are candidates for optoelectronic applications, have been gro... more Beryllium nitride thin films, which are candidates for optoelectronic applications, have been grown by pulsed laser deposition on silicon substrates. The films were prepared by ablating a beryllium foil in N environment at several pressures and substrate 2 temperatures. Real-time ellipsometric monitoring for the period of deposition were carried out by a multiwavelength ellipsometer in the 1.625(hn(4.405 eV photon-energy range. After its completion, the films were characterized in situ by electron spectroscopies and ex situ by atomic force and scanning electron microcopies. A model for the growth of beryllium nitride was applied to reproduce the optical measurement and concurrently, the refractive index from the visible to the near ultraviolet spectral region was calculated. The estimated optical bandgap correlates closely with previously published theoretical results. ᮊ
Applied Surface Science, 2003
Tungsten oxide thin films have been prepared by reactive pulsed laser deposition (PLD). Substrate... more Tungsten oxide thin films have been prepared by reactive pulsed laser deposition (PLD). Substrate heat treatment and oxygen partial pressure during growth are correlated with Auger electron (AES), X-ray photoelectron (XPS), electron energy loss (EELS) and ...
Diamond and Related Materials, 2003
A set of aluminium nitride (AlN), thin films were prepared by DC-reactive magnetron sputtering. T... more A set of aluminium nitride (AlN), thin films were prepared by DC-reactive magnetron sputtering. The deposition parameters, such as substrate temperature, sputtering gas composition and plasma current were varied. Spectroscopic ellipsometry, XPS, RBS, XRD, SEM, AFM and FTIR techniques were utilized to study the relationship between film properties and preparation conditions. We observed that the optical and surface properties have a strong dependence on the deposition rate. All prepared films present a composition close to AlN stoichiometry, even for nitrogen to argon gas concentrations below 1:2. The near surface of AlN films exposed to atmosphere was primarily composed of Al O while the bulk was AlN with some minor contamination of 2 3 oxygen and carbon. The thickness of the oxide layer was reduced when higher plasma current and lower nitrogen concentration were used. Deposits prepared at 400 8C presented the best refractive index and deposition rate, for both utilized plasma currents. ᮊ
Applied Surface Science, 2001
A series of samples were prepared by reactive laser ablation of a graphite target in nitrogen env... more A series of samples were prepared by reactive laser ablation of a graphite target in nitrogen environment. The CN x ®lms were annealed from room temperature to 900 8C, and in situ analyzed by electron energy loss spectroscopy (EELS), Auger electron spectroscopy, X-ray photoelectron spectroscopy and temperature desorption spectroscopy (TDS). A [N]/[C] ratio of 0.43 was determined and decreases notoriously as the annealing temperature increases. The peak shapes and intensities in the N 1s and C 1s regions are similar to those reported by other research groups. Small satellite peaks were observed in the N 1s and C 1s regions, corresponding to ®rst-and second-order inelastic energy losses of the main peaks. These losses were detected also by EELS with an energy of 4 eV and assigned to the p±p à plasmon. This resonance is distinctive of non-localized electrons in an sp 2 -hybridized carbon orbital. Thereafter, the main N 1s and C 1s peaks could be assigned to atoms in a six-and ®ve-member rings. Moreover, the ®lms were easily degraded by the thermal treatment and the main desorption product determined by TDS was found to be C 2 N 2 . We concluded that the most probable structure is one where N atoms dope graphite-like carbon layers by substitution, causing three-dimensional polymerization reactions, with chemical states similar to Upilex, Kapton and other polyimides. #
Solid State Communications, 1997
A process for obtaining Sro.3_3y/zLa,Bao,7Nbz06 (LSBN) ceramics at different concentrations of th... more A process for obtaining Sro.3_3y/zLa,Bao,7Nbz06 (LSBN) ceramics at different concentrations of the La3+ cation and different sintering times is presented. The dielectric properties of the LSBN system where Sr2+ ions are substituted by La3+ cations follow the pattern of a modification by cationic substitution for a constant Sr/Ba ratio. This behavior of the dielectric properties indicate that the La3+ cations occupy the A1 as well as the A2 sites which favors the formation of the LSBN system up to y c 0.05. For higher values the dielectric properties of the ceramic start to deteriorate. Copyright 0 1997 Published by Elsevier Science Ltd
Materials Letters, 2002
Beryllium nitride thin films were grown on silicon substrates by laser ablating a beryllium foil ... more Beryllium nitride thin films were grown on silicon substrates by laser ablating a beryllium foil in molecular nitrogen ambient. The composition and chemical state were determined with Auger (AES), X-Ray photoelectron (XPS) and energy loss (EELS) spectroscopies. A low absorption coefficient in the visible region, and an optical bandgap of 3.8 eV, determined by reflectance ellipsometry, were obtained for films grown at nitrogen pressures higher than 25 mTorr. The results show that the reaction of beryllium with nitrogen is very effective using this preparation method, producing high quality films.
Materials Letters, 2000
x y 3 4
Applied Surface Science, 1998
. In this work, thin films of SiCN have been deposited by pulsed laser deposition on silicon subs... more . In this work, thin films of SiCN have been deposited by pulsed laser deposition on silicon substrates by KrF 248 nm excimer laser ablation of a SiC sintered target in a vacuum system at room temperature. To obtain various stoichiometries, molecular nitrogen is introduced in the deposition chamber in the 5 to 500 mTorr pressure range. The resultant SiC N films
Applied Optics, 1990
Amorphous selenium films were produced by vacuum evaporation onto glass and aluminum substrates. ... more Amorphous selenium films were produced by vacuum evaporation onto glass and aluminum substrates. The chemical composition of the films and interfaces were studied using scanning Auger electron spectroscopy.
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 1997
Work is described on the fabrication of uncoated probe tips for reflection scanning near-field op... more Work is described on the fabrication of uncoated probe tips for reflection scanning near-field optical microscopes. A chemical etching process with a rotator, and a simple device to make the tips by a heating-pulling method without a heating laser are introduced. Both ...
Ferroelectrics, 1999
Abstract Pt thin films were deposited on Ti/Glass and TiO2/Si substrates by DC sputtering at temp... more Abstract Pt thin films were deposited on Ti/Glass and TiO2/Si substrates by DC sputtering at temperatures between room and 700° C to optimize its performance as electrodes for ferroelectric devices. Well oriented films in the (111) direction were obtained. Auger ...