Showing papers on "Scanning tunneling spectroscopy published in 2010"
TL;DR: Scanning tunneling Spectroscopy studies on high-quality Bi2Te3 crystals exhibit perfect correspondence to angle-resolved photoemission spectroscopy data, hence enabling identification of different regimes measured in the local density of states (LDOS).
Abstract: Scanning tunneling spectroscopy studies on high-quality Bi2Te3 crystals exhibit perfect correspondence to angle-resolved photoemission spectroscopy data, hence enabling identification of different regimes measured in the local density of states (LDOS). Oscillations of LDOS near a step are analyzed. Within the main part of the surface band oscillations are strongly damped, supporting the hypothesis of topological protection. At higher energies, as the surface band becomes concave, oscillations appear, dispersing with a wave vector that may result from a hexagonal warping term.
424 citations
TL;DR: Checkelsky et al. as mentioned in this paper investigated Dirac fermions on the surface of the topological insulator using scanning tunneling spectroscopy and found that a field-independent Landau level appears at the Dirac point.
Abstract: We investigate Dirac fermions on the surface of the topological insulator ${\text{Bi}}_{2}{\text{Se}}_{3}$ using scanning tunneling spectroscopy. Landau levels (LLs) are observed in the tunneling spectra in a magnetic field. In contrast to LLs of conventional electrons, a field-independent LL appears at the Dirac point, which is a hallmark of Dirac fermions. A scaling analysis of LLs based on the Bohr-Sommerfeld quantization condition allowed us to determine the dispersion of the surface band. Near the Fermi energy, fine peaks mixed with LLs appear in the spectra, which may be responsible for the anomalous magnetofingerprint effect [J. G. Checkelsky et al., Phys. Rev. Lett. 103, 246601 (2009)].
246 citations
TL;DR: This work investigates the spin- and energy-dependent tunneling through a single organic molecule (CoPc) adsorbed on a ferromagnetic Fe thin film, spatially resolved by low-temperature spin-polarized scanning tunneling microscopy.
Abstract: We investigate the spin- and energy-dependent tunneling through a single organic molecule (CoPc) adsorbed on a ferromagnetic Fe thin film, spatially resolved by low-temperature spin-polarized scanning tunneling microscopy. Interestingly, the metal ion as well as the organic ligand show a significant spin dependence of tunneling current flow. State-of-the-art ab initio calculations including also van der Waals interactions reveal a strong hybridization of molecular orbitals and substrate $3d$ states. The molecule is anionic due to a transfer of one electron, resulting in a nonmagnetic ($S=0$) state. Nevertheless, tunneling through the molecule exhibits a pronounced spin dependence due to spin-split molecule-surface hybrid states.
231 citations
TL;DR: In this paper, the Wentzel-Kramers-Brillouin (WKB) approximation and an atomistic, full-band quantum transport solver including direct and phonon-assisted tunneling (PAT) were used to simulate field effect transistors (TFETs).
Abstract: Nanowire band-to-band tunneling field-effect transistors (TFETs) are simulated using the Wentzel–Kramers–Brillouin (WKB) approximation and an atomistic, full-band quantum transport solver including direct and phonon-assisted tunneling (PAT). It is found that the WKB approximation properly works if one single imaginary path connecting the valence band (VB) and the conduction band (CB) dominates the tunneling process as in direct band gap semiconductors. However, PAT is essential in Si and Ge nanowire TFETs where multiple, tightly-coupled, imaginary paths exist between the VB and the CB.
191 citations
TL;DR: The bonded and the nonbonded state of the complex were found to be associated with different charge states, and the switching between the two states was accompanied by a considerable change in the tunneling current.
Abstract: We report on the formation of a metal-molecule complex that can be used as a molecular switch. Using a cryogenic scanning tunneling microscope, a covalent bond was formed reversibly between a gold atom and a perylene-3,4,9,10-tetracarboxylic dianhydride molecule supported by a thin insulating film. The bonded and the nonbonded state of the complex were found to be associated with different charge states, and the switching between the two states was accompanied by a considerable change in the tunneling current. Atomic force microscopy molecular imaging was employed to determine precisely the atomic structure of the complex, and the experimental results were corroborated by density functional theory calculations.
152 citations
TL;DR: In this paper, a semi-quantitative theory of electron pairing and resulting superconductivity in bulk "poor conductors" in which Fermi energy EF is located in the region of localized states not so far from the Anderson mobility edge Ec.
136 citations
TL;DR: In this article, the authors demonstrate the importance of coherent tunneling for large TMR with Heusler alloys with microfabricated epitaxial magnetic tunneling junctions.
Abstract: Spin-dependent coherent tunneling has been experimentally observed in high-quality sputtered-deposited ${\text{Co}}_{2}\text{FeAl}/\text{MgO}/\text{CoFe}$ epitaxial magnetic tunneling junctions (MTJs). Consequently, the microfabricated MTJs manifest a very large tunnel magnetoresistance (TMR) at room temperature and an unexpectedly TMR oscillation as a function of MgO barrier thickness. First-principles electronic band calculations confirm the pronounced coherent tunneling effect and are in good agreement with the experimental data. The present work demonstrates the importance of coherent tunneling for large TMR with Heusler alloys
135 citations
TL;DR: A scanning tunneling microscope (STM) has been equipped with a nanoscale force sensor and signal transducer composed of a single D2 molecule that is confined in the STM junction that probes the short-range Pauli repulsion and converts this signal into variations of the junction conductance.
Abstract: A scanning tunneling microscope (STM) has been equipped with a nanoscale force sensor and signal transducer composed of a single ${\mathrm{D}}_{2}$ molecule that is confined in the STM junction. The uncalibrated sensor is used to obtain ultrahigh geometric image resolution of a complex organic molecule adsorbed on a noble metal surface. By means of conductance-distance spectroscopy and corresponding density functional calculations the mechanism of the sensor and transducer is identified. It probes the short-range Pauli repulsion and converts this signal into variations of the junction conductance.
134 citations
TL;DR: In this article, a combined multimethod experimental and theoretical study of the geometric and electronic properties of Co-tetraphenyl-porphyrin Co-TPP molecules adsorbed on a Ag111 surface is presented.
Abstract: We present a combined multimethod experimental and theoretical study of the geometric and electronic properties of Co-tetraphenyl-porphyrin Co-TPP molecules adsorbed on a Ag111 surface. Scanning tunneling microscopy STM topographs reveal that Co-TPP forms highly regular arrays with a square unit cell. Hereby, the Co-TPP molecules do not occupy a unique adsorption site on the Ag111 atomic lattice. The central Co atom of the Co-TPP is found to reside predominantly above fcc and hcp hollow sites of the substrate, as determined from the photoelectron diffraction patterns. A strong adsorption-induced deformation of Co-TPP involving a saddle-shaped macrocycle is evidenced by high-resolution STM images and quantified by near-edge x-ray absorption fine-structure measurements. By scanning tunneling spectroscopy we resolved discrete molecular electronic states and mapped the pertaining spatial charge-density distribution. Specifically, we discuss the interaction of orbitals originating from the Co-metal center with the porphyrin macrocycle and show that the varying adsorption sites induce a modulation in the Co-TPP lowest unoccupied molecular orbital. These findings are corroborated by density-functional-theory calculations.
132 citations
TL;DR: Topographies of different edge structures of monolayer graphene show that the localization of the electronic density of states along the C-C bonds results in quantum interference patterns along the graphene carbon bond network, whose shapes depend only on the edge structure and not on the electron energy.
Abstract: Electron scattering at graphene edges is expected to make a crucial contribution to the electron transport in graphene nanodevices by producing quantum interferences. Atomic-scale scanning tunneling microscopy (STM) topographies of different edge structures of monolayer graphene show that the localization of the electronic density of states along the C-C bonds, a property unique to monolayer graphene, results in quantum interference patterns along the graphene carbon bond network, whose shapes depend only on the edge structure and not on the electron energy.
112 citations
TL;DR: Study of electronic properties and scanning tunneling microscopy of the most common configurations of nitrogen- or boron-doped graphene and carbon nanotubes using density functional theory shows common fingerprints for the same doping type for graphene, and metallic or semiconducting nanot tubes.
Abstract: We report on studies of electronic properties and scanning tunneling microscopy (STM) of the most common configurations of nitrogen- or boron-doped graphene and carbon nanotubes using density functional theory. Charge transfer, shift of the Fermi level, and localized electronic states are analyzed as a function of the doping configurations and concentrations. The theoretical STM images show common fingerprints for the same doping type for graphene, and metallic or semiconducting nanotubes. In particular, nitrogen is not imaged in contrast to boron. STM patterns are mainly shaped by local density of states of the carbon atoms close to the defect. STM images are not strongly dependent on the bias voltage when scanning the defect directly. However, the scanning of the defect-free side of the tube displays a perturbation compared to the pristine tube depending on the applied bias.
TL;DR: Using a straightforward model, theoretical tunneling spectra are calculated that agree well with data, providing insight into the effects of many-body interactions on the lifetime of graphene quasiparticles.
Abstract: We find the scanning tunneling spectra of backgated graphene monolayers to be significantly altered by many-body excitations. Experimental features in the spectra arising from electron-plasmon interactions show carrier density dependence, distinguishing them from density-independent electron-phonon features. Using a straightforward model, we are able to calculate theoretical tunneling spectra that agree well with our data, providing insight into the effects of many-body interactions on the lifetime of graphene quasiparticles.
IBM1
TL;DR: In this paper, the spin dependence of elastic and inelastic electron tunneling through transition metal atoms was investigated and it was shown that the additional conservation of spin angular momentum leads to different cross-sections for spin excitations depending on the relative alignment of the surface spin and the spin of the tunneling electron.
Abstract: We report on the spin dependence of elastic and inelastic electron tunneling through transition metal atoms. Mn, Fe and Cu atoms were deposited onto a monolayer of Cu2N on Cu(100) and individually addressed with the probe tip of a scanning tunneling microscope. Electrons tunneling between the tip and the substrate exchange energy and spin angular momentum with the surface-bound magnetic atoms. The conservation of energy during the tunneling process results in a distinct onset threshold voltage above which the tunneling electrons create spin excitations in the Mn and Fe atoms. Here we show that the additional conservation of spin angular momentum leads to different cross-sections for spin excitations depending on the relative alignment of the surface spin and the spin of the tunneling electron. For this purpose, we developed a technique for measuring the same local spin with a spin-polarized and a non-spin-polarized tip by exchanging the last apex atom of the probe tip between different transition metal atoms. We derive a quantitative model describing the observed excitation cross-sections on the basis of an exchange scattering process.
TL;DR: Visible and infrared light emitted at a Ag-Ag(111) junction has been investigated from tunneling to single-atom contact conditions with a scanning tunneling microscope in terms of current noise at optical frequencies, which is characteristic of partially open transport channels.
Abstract: Visible and infrared light emitted at a Ag-Ag(111) junction has been investigated from tunneling to single-atom contact conditions with a scanning tunneling microscope. The light intensity varies in a highly nonlinear fashion with the conductance of the junction and exhibits a minimum at conductances close to the conductance quantum. The data are interpreted in terms of current noise at optical frequencies, which is characteristic of partially open transport channels.
TL;DR: It is shown that dI/dV directly reflects the strength of the antiferromagnetic interaction in Kondo lattice systems.
Abstract: We present a large-N theory for the differential conductance, dI/dV, in Kondo systems measured via scanning tunneling spectroscopy. We demonstrate that quantum interference between tunneling processes into the conduction band and into the magnetic f-electron states is crucial in determining the experimental Fano line shape of dI/dV. This allows one to uniquely extract the Kondo coupling and the ratio of the tunneling amplitudes from the experimental dI/dV curve. Finally, we show that dI/dV directly reflects the strength of the antiferromagnetic interaction in Kondo lattice systems.
TL;DR: Low-temperature, ultrahigh vacuum scanning tunneling microscopy is used to investigate the atomic-scale geometry of Pd/Au111 near-surface alloys and to spectroscopically probe their local electronic structure, revealing that in both surface and subsurface locations, Pd atoms display a very similar electronic structure to the surrounding Au atoms.
Abstract: Pd/Au bimetallic alloys catalyze many important reactions ranging from the synthesis of vinyl acetate and hydrogen peroxide to the oxidation of carbon monoxide and trimerization of acetylene. It is known that the atomic-scale geometry of these alloys can dramatically affect both their reactivity and selectivity. However, there is a distinct lack of experimental characterization and quantification of ligand and ensemble effects in this system. Low-temperature, ultrahigh vacuum scanning tunneling microscopy is used to investigate the atomic-scale geometry of Pd/Au111 near-surface alloys and to spectroscopically probe their local electronic structure. The results reveal that the herringbone reconstruction of Au111 provides entry sites for the incorporation of Pd atoms in the Au surface and that the degree of mixing is dictated by the surface temperature. At catalytically relevant temperatures the distribution of low coverages of Pd in the alloy is random, except for a lack of nearest neighbor pairs in both the surface and subsurface sites. Scanning tunneling spectroscopy is used to examine the electronic structure of the individual Pd atoms in surface and subsurface sites. This work reveals that in both surface and subsurface locations, Pd atoms display a very similar electronic structure to the surrounding Au atoms. However, individual surface and subsurface Pd atoms are depleted of charge in a very narrow region at the band edge of the Au surface state. dI/dV images of the phenomena demonstrate the spatial extent of this electronic perturbation.
TL;DR: Single tetracyanoethyelene molecules on Cu(111) are reversibly switched among five states by applying voltage pulses with the tip of a scanning tunneling microscope, indicating that one of the states is magnetic.
Abstract: Single tetracyanoethyelene (TCNE) molecules on Cu(111) are reversibly switched among five states by applying voltage pulses with the tip of a scanning tunneling microscope. A pronounced Kondo resonance in tunneling spectroscopy indicates that one of the states is magnetic. Side bands of the Kondo resonance appear at energies which correspond to inter- and intramolecular vibrational modes. Density functional theory suggests that molecular deformation changes the occupancy in TCNE’s molecular orbitals, thus producing the magnetic state.
TL;DR: In this paper, a comparison between the electronic structures determined in ultrahigh vacuum of three surfaces using scanning tunneling spectroscopy (STS) and Kelvin probe force microscopy (KPFM) is made.
Abstract: A comparison is made between the electronic structures determined in ultrahigh vacuum of three surfaces using scanning tunneling spectroscopy (STS) and Kelvin probe force microscopy (KPFM). STS and KPFM illustrates Fermi level pinning of clean InAs(001)-(4×2) and InGaAs(001)-(4×2) surfaces and near flat band conditions for InAs(110) cleaved surfaces. However, for InAs(001)-(4×2) and InGaAs(001)-(4×2), STS and KPFM data show very different positions for the surface Fermi level on identical samples; it is hypothesized that the difference is due to the Fermi level measured by KPFM being shifted by a static charge dipole to which STS is much less sensitive.
TL;DR: The morphology and electronic structure of monolayer graphene grown on the (111) and (110) facets of three-dimensional nickel islands on highly oriented pyrolytic graphite substrate point to the possibility of preparing large-area epitaxial graphene layers even on polycrystalline Ni substrates.
Abstract: Using scanning tunneling microscopy and spectroscopy, in combination with density functional theory calculations, we investigated the morphology and electronic structure of monolayer graphene grown on the (111) and (110) facets of three-dimensional nickel islands on highly oriented pyrolytic graphite substrate. We observed graphene domains exhibiting hexagonal and striped moire patterns with periodicities of 22 and 12 A, respectively, on (111) and (110) facets of the Ni islands. Graphene domains are also observed to grow, as single crystals, across adjacent facets and over facet boundaries. Scanning tunneling spectroscopy data indicate that the graphene layers are metallic on both Ni(111) and Ni(110), in agreement with the calculations. We attribute this behavior to a strong hybridization between the d-bands on Ni and the π-bands of carbon. Our findings point to the possibility of preparing large-area epitaxial graphene layers even on polycrystalline Ni substrates.
TL;DR: It is shown that inelastic intermolecular scattering is important in the SAM by plotting the theoretical current densities, and the calculations agree quantitatively with the measured IETS in producing the weight of the symmetric and asymmetric C-H stretch modes.
Abstract: We investigate inelastic electron tunneling spectroscopy (IETS) for alkanethiol self-assembled monolayers (SAM) with a scanning tunneling microscope and compare it to first-principles calculations. Using a combination of partial deuteration of the molecule and high-resolution measurements, we identify and differentiate between methyl (${\mathrm{CH}}_{3}$) and methylene (${\mathrm{CH}}_{2}$) groups and their symmetric and asymmetric C-H stretch modes. The calculations agree quantitatively with the measured IETS in producing the weight of the symmetric and asymmetric C-H stretch modes while the methylene stretch mode is largely underestimated. We further show that inelastic intermolecular scattering is important in the SAM by plotting the theoretical current densities.
TL;DR: A photonic analog of Klein tunneling for a relativistic electron across a potential step, based on spatial light propagation in an engineered binary waveguide array, is proposed in this paper.
Abstract: A photonic analog of Klein tunneling for a relativistic electron across a potential step, based on spatial light propagation in an engineered binary waveguide array, is proposed. Klein tunneling can be simply visualized as optical beam refraction through a step-index interface, superimposed to the superlattice, and explained as an interband tunneling process between positive-energy (electron) and negative-energy (positron) minibands of the superlattice. Inhibition of Klein tunneling for a smooth potential step is also demonstrated.
TL;DR: A significant BN-to-graphene charge donation is evident in the electronic structure of a graphene/h-BN(0001) heterojunction grown by chemical vapor deposition and atomic layer deposition directly on Ru(0001), consistent with density functional theory.
Abstract: A significant BN-to-graphene charge donation is evident in the electronic structure of a graphene/h-BN(0001) heterojunction grown by chemical vapor deposition and atomic layer deposition directly on Ru(0001), consistent with density functional theory. This filling of the lowest unoccupied state near the Brillouin zone center has been characterized by combined photoemission/k vector resolved inverse photoemission spectroscopies, and Raman and scanning tunneling microscopy/spectroscopy. The unoccupied σ*(Γ(1) +) band dispersion yields an effective mass of 0.05 m(e) for graphene in the graphene/h-BN(0001) heterostructure, in spite of strong perturbations to the graphene conduction band edge placement.
TL;DR: In this paper, the authors studied the tunneling current in InGaN/GaN multiquantum-well blue light-emitting diodes grown on sapphire substrate and found that tunneling currents vary approximately as a function of ∼exp(−βEg+λeV), where β and λ are constants independent of temperature and voltage.
Abstract: Forward tunneling current in InGaN/GaN multiquantum-well blue light-emitting diodes grown on sapphire substrate was studied by temperature-variable current-voltage (I-V) measurement. All semilog I-V curves obtained in the temperature range from 100 to 300 K exhibit two successive linearly dependent regions at low forward bias. The corresponding slopes appear to be insensitive to temperature, which indicates a dominant defect-assisted tunneling process. It is found that the tunneling current varies approximately as a function of ∼exp(−βEg+λeV), where β and λ are constants independent of temperature and voltage. The temperature- and voltage-dependence of forward tunneling current are explained by thermally induced band gap shrinkage and bias-induced route change of diagonal tunneling, respectively. The likely tunneling entities involved in the forward tunneling process are also discussed.
TL;DR: This study shows the feasibility of a bistable single molecule switch on an insulator by scanning tunneling microscopy and a reversible isomerization between a planar trans and a three-dimensional cis form with two different thresholds.
Abstract: Scanning tunneling microscopy is used to investigate isomerization of amino-nitro-azobenzene on a thin NaCl layer on Ag(111) by inelastically tunneling electrons. A reversible isomerization between a planar trans and a three-dimensional cis form with two different thresholds is demonstrated. The isomerization characteristics are rationalized in terms of binding of the multipolar molecule to the ionic layer. This study shows the feasibility of a bistable single molecule switch on an insulator.
TL;DR: GXSM is a full featured and modern scanning probe microscopy (SPM) software that can be used for powerful multidimensional image/data processing, analysis, and visualization.
Abstract: GXSM is a full featured and modern scanning probe microscopy (SPM) software. It can be used for powerful multidimensional image/data processing, analysis, and visualization. Connected to an instrument, it is operating many different flavors of SPM, e.g., scanning tunneling microscopy and atomic force microscopy or, in general, two-dimensional multichannel data acquisition instruments. The GXSM core can handle different data types, e.g., integer and floating point numbers. An easily extendable plug-in architecture provides many image analysis and manipulation functions. A digital signal processor subsystem runs the feedback loop, generates the scanning signals, and acquires the data during SPM measurements. The programmable GXSM vector probe engine performs virtually any thinkable spectroscopy and manipulation task, such as scanning tunneling spectroscopy or tip formation. The GXSM software is released under the GNU general public license and can be obtained via the internet.
TL;DR: Tin-phthalocyanine molecules adsorbed on Ag(111) were contacted with the tip of a cryogenic scanning tunneling microscope and Nonequilibrium Green's function calculations reproduce the trend of the conductance and visualize the current flow through the junction, which is guided through molecule-electrode chemical bonds.
Abstract: Tin-phthalocyanine molecules adsorbed on Ag(111) were contacted with the tip of a cryogenic scanning tunneling microscope. Orders-of-magnitude variations of the single-molecule junction conductance were achieved by controllably dehydrogenating the molecule and by modifying the atomic structure of the surface electrode. Nonequilibrium Green's function calculations reproduce the trend of the conductance and visualize the current flow through the junction, which is guided through molecule-electrode chemical bonds.
TL;DR: In this article, the authors investigated the chemical doping of epitaxial graphene (EG) by organic free radicals (4-amino-2,2,6, 6,6-tetramethyl-1-piperridinyloxy; 4aminoTEMPO) using scanning tunneling microscopy (STM) and high resolution photoemission spectroscopy (HRPES).
Abstract: Chemical doping of epitaxial graphene (EG) by organic free radicals (4-amino-2,2,6,6-tetramethyl-1-piperridinyloxy; 4-amino-TEMPO) was investigated using scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and high resolution photoemission spectroscopy (HRPES). STM images revealed that the empty density of states near the adsorption site significantly decreased as a result of radical doping. STS indicated that 4-amino-TEMPO radicals acted as n-type dopants on monolayer graphene. The radicals adsorbed onto EG through the nitroxide groups, leaving the amine group unreacted, which was confirmed by the binding energies of N 1s and O 1s core-level spectra. Furthermore, the measured work function changes verified that increased adsorption of the radicals on EG showed n-type doping characteristics.
TL;DR: Graphene crossbar structures fabricated in stacked configurations demonstrate the versatility of the procedures and sheet resistances determined from measurements of four point probe devices were found to be ∼2 kΩ/square, close to expectation.
Abstract: Here we report a technique for transferring graphene layers, one by one, from a multilayer deposit formed by epitaxial growth on the Si-terminated face of a 6H-SiC substrate. The procedure uses a bilayer film of palladium/polyimide deposited onto the graphene coated SiC, which is then mechanically peeled away and placed on a target substrate. Orthogonal etching of the palladium and polyimide leaves isolated sheets of graphene with sizes of square centimeters. Repeating these steps transfers additional sheets from the same SiC substrate. Raman spectroscopy, scanning tunneling spectroscopy, low-energy electron diffraction and X-ray photoelectron spectroscopy, together with scanning tunneling, atomic force, optical, and scanning electron microscopy reveal key properties of the materials. The sheet resistances determined from measurements of four point probe devices were found to be ∼2 kΩ/square, close to expectation. Graphene crossbar structures fabricated in stacked configurations demonstrate the versatilit...
TL;DR: In this article, the electronic properties of edge and corner atoms of planar Au clusters on MgO/Ag(001) thin films have been analyzed with scanning tunneling microscopy and electronic structure calculations.
Abstract: The perimeter of oxide-supported metal particles is suggested to be of pivotal importance for various catalytic processes. To elucidate the underlying effects, the electronic properties of edge and corner atoms of planar Au clusters on MgO/Ag(001) thin films have been analyzed with scanning tunneling microscopy and electronic structure calculations. The low-coordinated perimeter atoms are characterized by a high density of $s$-derived states at the Fermi level. Those states accommodate transfer electrons from the MgO/Ag substrate, which render the perimeter atoms negatively charged. In contrast, the inner atoms of the island are not affected by the charge transfer and remain neutral. This combination of charge accumulation and high state-density explains the specific relevance of the cluster perimeter in adsorption and reaction processes.
TL;DR: In this paper, a detailed bias-dependent study of the spatial magnetic sensitivity on the system of 1.5 monolayers of Fe/W(110) reveals that all magnetic directions in space are sensed over a wide bias range, thereby indicating a canted magnetization direction being a typical feature of bulk Cr tips.
Abstract: A full magnetic characterization of bulk Cr tips has been achieved using spin-polarized scanning tunneling microscopy at low temperature. A detailed bias-dependent study of the spatial magnetic sensitivity on the system of 1.5 monolayers of Fe/W(110) reveals that all magnetic directions in space are sensed over a wide bias range, thereby indicating a canted magnetization direction being a typical feature of bulk Cr tips. Consequently, using Cr as tip material allows any standard scanning tunneling microscope setup to be extended by the spin-polarized mode.