Surface photovoltage in semiconductors under pulsed optical excitation, and its relevance to synchrotron radiation spectroscopy

Marsi, M.; Nahon, Laurent; Couprie, M.E.; Garzella, D.; Hara, Toru; Bakker, R.J.; Billardon, M.; Delboulbé, A.; Indlekofer, G.; Taleb‐Ibrahimi, A.

doi:10.1016/s0368-2048(98)00142-x

Cited by 31 publications

(14 citation statements)

References 19 publications

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“…This charge disequilibrium at the surface explains the unusually long relaxation time for Bi 2.2 Te 3 (excess electrons find no holes to recombine with), as well as its temperature dependence (the bulk mobility of the carriers is lower at 40 K than at 130 K due to impurity scattering). The corresponding transient surface photovoltage 30,31 was measured for the various time delays (Supplementary Figure S3) and found to be negligibly small (≈ 10 meV) for the laser fluences used in this study.…”

Section: Resultsmentioning

confidence: 87%

Tuning a Schottky barrier in a photoexcited topological insulator with transient Dirac cone electron-hole asymmetry

et al. 2014

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The advent of Dirac materials has made it possible to realize two-dimensional gases of relativistic fermions with unprecedented transport properties in condensed matter. Their photoconductive control with ultrafast light pulses is opening new perspectives for the transmission of current and information. Here we show that the interplay of surface and bulk transient carrier dynamics in a photoexcited topological insulator can control an essential parameter for photoconductivity-the balance between excess electrons and holes in the Dirac cone. This can result in a strongly out of equilibrium gas of hot relativistic fermions, characterized by a surprisingly long lifetime of more than 50 ps, and a simultaneous transient shift of chemical potential by as much as 100 meV. The unique properties of this transient Dirac cone make it possible to tune with ultrafast light pulses a relativistic nanoscale Schottky barrier, in a way that is impossible with conventional optoelectronic materials.

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Section: Resultsmentioning

confidence: 87%

Tuning a Schottky barrier in a photoexcited topological insulator with transient Dirac cone electron-hole asymmetry

et al. 2014

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“…However, specific difficulties arise in the interpretation of the data in the case of Si(111)-7×7 that explain the conflicting results of the literature. The surface photovoltage (SPV) effect 45,46 introduces in the low-temperature photoemission spectra an indeterminacy of the E F position of at least several tens of meV. This energy scale is critical for the Si(111)-7×7 surface and makes different datasets compatible with a metallic 16,18,20 or insulating 17 ground state.…”

Section: Introductionmentioning

confidence: 99%

Low-temperature insulating phase of the Si(111)–7×7 surface

et al. 2020

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We investigated the electronic structure of the Si(111)-7×7 surface below 20 K by scanning tunneling and photoemission spectroscopies and by density functional theory calculations. Previous experimental studies have questioned the ground state of this surface, which is expected to be metallic in a band picture because of the odd number of electrons per unit cell. Our differential conductance spectra instead show the opening of an energy gap at the Fermi level and a significant temperature dependence of the electronic properties, especially for the adatoms at the center of the unfaulted half of the unit cell. Complementary photoemission spectra with improved correction of the surface photovoltage shift corroborate the differential conductance data and demonstrate the absence of surface bands crossing the Fermi level at 17 K. These consistent experimental observations point to an insulating ground state and contradict the prediction of a metallic surface obtained by density functional theory in the generalized gradient approximation. The calculations indicate that this surface has or is near a magnetic instability, but remains metallic in the magnetic phases even including correlation effects at mean-field level. We discuss possible origins of the observed discrepancies between experiments and calculations.

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“…In conventional data gathering mode the sample is grounded, and the position as well as the intensity of the peaks are recorded in a static fashion [20]. Although several reports have appeared in the literature related to dynamical XPS measurements in the two extreme ends, very fast (nanoseconds to attoseconds) [21][22][23][24], and very slow (minutes to hours) [25][26][27] through various publications, the basic principles and techniques for implementing such measurements employing very simple modification to conventional instruments [28][29][30][31][32][33][34][35][36][37][38][39].…”

Section: Introductionmentioning

confidence: 99%

XPS for probing the dynamics of surface voltage and photovoltage in GaN

Sezen¹,

Özbay²,

Süzer³

2014

Applied Surface Science

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a b s t r a c tWe describe application of two different data gathering techniques of XPS for probing the dynamics of surface voltage and surface photovoltage (SPV) developed in microseconds to seconds time-domain, in addition to the conventional steady-state measurements. For the longer (seconds to milliseconds) regime, capturing the data in the snapshot fashion is used, but for the faster one (down to microseconds), square wave (SQW) electrical pulses at different frequencies are utilized to induce and probe the dynamics of various processes causing the surface voltage, including the SPV, via the changes in the peak positions. The frequency range covers anywhere from 10 −3 to 10 5 Hz for probing changes due to charging (slow), dipolar (intermediate), and electronic (fast) processes associated with the external stresses imposed. We demonstrate its power by application to n-and p-GaN, and discuss the chemical/physical information derived thereof. In addition, the method allows us to decompose and identify the peaks with respect to their charging nature for a composite sample containing both n-and p-GaN moieties.

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Surface photovoltage in semiconductors under pulsed optical excitation, and its relevance to synchrotron radiation spectroscopy

Cited by 31 publications

References 19 publications

Tuning a Schottky barrier in a photoexcited topological insulator with transient Dirac cone electron-hole asymmetry

Tuning a Schottky barrier in a photoexcited topological insulator with transient Dirac cone electron-hole asymmetry

Low-temperature insulating phase of the Si(111)–7×7 surface

XPS for probing the dynamics of surface voltage and photovoltage in GaN

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