Near-field magneto-optical imaging in scanning tunneling microscopy

Prins, Mwj Menno; Groeneveld, R.H.M.; Abraham, D. L.; Kempen, H. van; Kesteren, HW van

doi:10.1063/1.113839

Cited by 42 publications

(19 citation statements)

References 10 publications

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“…Magnetic imaging can be achieved in two distinct ways, namely, by magneto-optical near-field imaging 8 and by spin-polarized tunneling due to optical spin-orientation. [9][10][11] In magnetooptical imaging, the semiconductor tip operates as a local photodetector that maps the polarization-dependent optical properties of a magnetic material.…”

Section: Discussionmentioning

confidence: 99%

“…From the previous data, we conclude that a semiconductor tunneling tip can be very sensitive to optical excitation, making these tips interesting as scanning local photodetectors 8 and as sources of optically oriented spin-polarized electrons. 9,10 However, because a STM is normally operated in the constant-current mode, the frequency band between zero and about 2 kHz is used for stabilization of the tip-to-sample distance.…”

Section: Modulated Photoexcitationmentioning

confidence: 99%

“…When used for topographical imaging in a STM, these tips yield a resolution close to a nanometer under ambient conditions. 8,10 The GaAs was n type ͑Si doped͒ or p type ͑Zn doped͒, with doping densities ranging from 10 22 m Ϫ3 to 5ϫ10 23 m Ϫ3 . The bandwidth of the STM constant-current regulation circuit was set between one and two kilohertz.…”

Section: Methodsmentioning

confidence: 99%

“…Photoexcited STM studies have been conducted with the semiconductor material as the sample, 4 but more recently also as a tip material photoexcited semiconductors have been subjected to investigation. 5 Ϫ7 These tips hold special attraction with regard to near-field optical imaging 8 and as sources of optically oriented spin-polarized electrons. [9][10][11] In this paper, we intend to develop a thorough understanding of the current transport properties of photoexcited semiconductor materials in the STM.…”

Section: Introductionmentioning

confidence: 99%

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Photoelectrical properties of semiconductor tips in scanning tunneling microscopy

Prins¹,

Jansen²,

Groeneveld³

et al. 1996

Phys. Rev. B

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We describe a model as well as experiments on the electrical properties of a photoexcited tunnel junction between a metal and a semiconductor material, as is established in a scanning tunneling microscope. The model treats the case in which carrier transport is mediated by capture and relaxation in the semiconductor surface states. In the semiconductor, majority carrier transport is determined by thermionic emission over the Schottky barrier and subsequent surface recombination. By optical excitation an additional minority carrier current is generated. The voltage that develops on the semiconductor surface is determined by the balance between majority and minority carrier current in the semiconductor, and the current across the tunnel barrier. We present model calculations of the ͑nonplanar͒ band-bending profile in the semiconductor, which indicate that the subsurface electric field operates as an electrical lens that can focus or defocus the current. Measurements were performed with moderately doped GaAs tips or samples prepared by cleavage. Continuous as well as modulated photoexcitation was used. Relationships are determined between tunnel current, applied voltage, incident optical power, and tip-sample distance. The experimental results are well described by the model that includes carrier capture in the semiconductor surface states. It is shown that the sensitivity of the tunnel current to small variations in optical power is determined by the ratio of the tunnel barrier conductance to the Schottky barrier conductance. The implications for near-field optical imaging and spin-polarized tunneling with semiconductor tips are discussed.

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Section: Discussionmentioning

confidence: 99%

Section: Modulated Photoexcitationmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Photoelectrical properties of semiconductor tips in scanning tunneling microscopy

Prins¹,

Jansen²,

Groeneveld³

et al. 1996

Phys. Rev. B

Self Cite

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“…This has already been shown experimentally to facilitate imaging of prewritten magnetic bits in a Pt/Co multilayer sample with STM. 41 With regard to material parameters that control the size of , thereby introducing additional uncertainties. It is therefore best to have experimental conditions such that Eq.…”

Section: Discussionmentioning

confidence: 99%

Theory of spin-polarized transport in photoexcited semiconductor/ferromagnet tunnel junctions

1998

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We present a theory for spin-polarized transport in tunnel junctions consisting of a ferromagnet and a semiconductor, in which spin-polarized carriers are created by optical orientation. The model includes, for both spin orientations, the current due to tunneling between the ferromagnet and the semiconductor surface as well as the photoinduced and the thermionic emission currents through the semiconductor subsurface region. Tunneling is described in terms of a spin-dependent tunnel conductance, taking account of the magnetic structure of the ferromagnet. We consider spin depolarization of photoexcited electrons in the semiconductor bulk material and in surface states that have a spin-dependent occupation. The total tunnel current is evaluated as well as current modulations due to modulated spin polarization of photoelectrons ͑CPM signal͒ or modulated optical intensity. The calculations show that the CPM signal is proportional to the tunnel conductance polarization and is relatively insensitive to spin depolarization of photoelectrons during their transport to the surface. A severe signal reduction can, however, result from spin relaxation in semiconductor surface states. In addition, it is demonstrated that a crucial role is played by the operating regime of the junction, i.e., photoamperic or photovoltaic, where the selection is determined mainly by the choice of applied bias voltage. We find that the photovoltaic mode is favored, as it yields the highest contribution from spin-polarized tunneling, combined with the smallest sensitivity for unwanted light intensity modulations. ͓S0163-1829͑98͒03207-X͔

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Scanning Near-field Magneto-optic Microscopy: Quantitative Measurements of Local Faraday Effects

Eggers

Rosenberger

Held

et al. 1997

Surf. Interface Anal.

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The implementation of a phase‐modulating polarization detector into a scanning near‐field optical microscope allows the imaging of local magneto‐optic effects with spatial resolution. By taking several pictures at the same location with different detector settings, a quantitative evaluation of magneto‐optic effects, such as Faraday rotation, becomes possible. Images were taken from thin garnet films using this method.©1997 John Wiley & Sons, Ltd.

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Near-field magneto-optical imaging in scanning tunneling microscopy

Cited by 42 publications

References 10 publications

Photoelectrical properties of semiconductor tips in scanning tunneling microscopy

Photoelectrical properties of semiconductor tips in scanning tunneling microscopy

Theory of spin-polarized transport in photoexcited semiconductor/ferromagnet tunnel junctions

Scanning Near-field Magneto-optic Microscopy: Quantitative Measurements of Local Faraday Effects

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