Ultrafast Carrier Dynamics in Silicon: A Two-Color Transient Reflection Grating Study on a<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mo>(</mml:mo><mml:mn>111</mml:mn><mml:mo>)</mml:mo></mml:math>Surface

Sjodin, Theodore; Petek, Hrvoje; Dai, Hai‐Lung

doi:10.1103/physrevlett.81.5664

Cited by 189 publications

(106 citation statements)

References 20 publications

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“…By varying the time in-between 266 nm pump and THz probe pulses, we initially observe a rise in the magnitude of ⌬E ͑see inset of Fig. 1͒ which we attribute to cooling of the nascent hot electrons and holes to their respective band edges ͑which typically takes a few picoseconds 13 ͒. Below, we present measurements of ⌬E͑t͒ 10 ps after excitation-sufficiently long to allow for thermalization and cooling of hot charges but fast enough to minimize diffusive expansion of the plasma 14 or carrier trapping and/or recombination, which occurs on nanosecond time scales.…”

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confidence: 93%

Reduction of carrier mobility in semiconductors caused by charge-charge interactions

et al. 2007

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We investigate the effect of charge-charge interactions on carrier mobility in titanium dioxide ͑TiO 2 ͒ and silicon ͑Si͒ using terahertz spectroscopy. Charge scattering times and plasma frequencies are directly determined as a function of charge density. In Si, a linear increase in scattering rate for densities exceeding 10 21 m −3 is attributed to electron-hole scattering. In contrast, in TiO 2 , charge-charge interactions are suppressed due to dielectric screening, highlighting the vastly different dielectric properties for these two materials. DOI: 10.1103/PhysRevB.75.233202 PACS number͑s͒: 72.40.ϩw, 72.10.Di, 72.20.Dp Charge-charge interactions determine many of the properties of highly doped or photoexcited semiconductors. Carrier-carrier collisions, for instance, can strongly affect the conductivity, and the decrease of electron and hole drift mobilities with increasing charge carrier densities is an important factor in determining the current-voltage characteristics of, for example, semiconductor diodes at increased current densities 1 and solar cells under strong illumination conditions. 2 Charge mobility depends on two quantities: its effective mass and scattering time ͑i.e., the average time in-between momentum-randomizing events, due to, e.g., electronphonon scattering͒. Theory has indicated that both of these quantities can be strongly dependent on the free charge density in semiconductors. [3][4][5] Experimental investigations of carrier-carrier interactions are, however, intrinsically more complex, as most experimental techniques ͑such as optical reflectivity measurements 6,7 ͒ cannot easily distinguish between changes in scattering time and effective mass. Terahertz time-domain spectroscopy ͑THz-TDS͒, with its ability to determine both the real and imaginary components of the complex conductivity, 8 allows us to differentiate between density-dependent changes in effective mass from changes in scattering time.Here, we compare the high-density photoconductivity of single crystal silicon ͑Si͒ and rutile-type titanium dioxide ͑TiO 2 ͒, two technologically relevant materials with low and high dielectric functions, respectively. By photoexciting with intense, femtosecond ultraviolet laser pulses and probing with THz pulses, we can generate and measure high-density plasmas in semiconductors on ultrafast time scales, accessing plasma densities spanning 5 orders of magnitude from 10 21 to 10 26 m −3 . In Si, we find that the scattering rate increases linearly for densities Ͼ10 21 m −3 , an effect characteristic of direct charge-charge scattering. For TiO 2 , the variation of the scattering rate with density is much weaker and is caused by band filling effects. The difference between these two materials is shown to originate from their vastly different dielectric screening properties.The TiO 2 ͑1 mm thick 001 rutile crystal grown commercially by the Verneuil method by Crystal-GmbH͒ and silicon ͑0.5 mm thick undoped Si wafer, grown by the Czochralski method with estimated impurity density Ͻ10 13 cm −3 ,...

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confidence: 93%

Reduction of carrier mobility in semiconductors caused by charge-charge interactions

et al. 2007

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“…9,10 TR-2PPE has frequently been used for analyzing electron dynamics at metal surfaces, in particular the dynamics of image potential states, adatoms, and small molecules. [11][12][13] Work on semiconductor surfaces has mainly concentrated on silicon 14,15 and on hot electron dynamics at the surface of III-V semiconductors. 16,17 We report here on the time-dependent escape of photogenerated electrons from the surface into the bulk of rutile TiO 2 ͑110͒.…”

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confidence: 99%

Escape dynamics of photoexcited electrons at catechol:TiO2(110)

2006

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Ultrafast electron escape dynamics following excitation of the interfacial charge transfer complex of catechol prepared on the rutile TiO 2 ͑110͒ surface was investigated with femtosecond two-photon photoemission ͑2PPE͒. Laser pulses were generated with two noncollinear optical parametric amplifiers operated simultaneously at a repetition rate of 150 kHz delivering a cross-correlation function with 35 fs full width at half maximum. Catechol was absorbed from the solution. The experimental data were not depending on the choice between three different solvents. Photoinduced interfacial charge transfer was instantaneous and thus the rise of the signal was controlled by the cross-correlation function. The energy distribution of the hot electrons generated at the surface was measured as 2PPE spectrum. The decay of the 2PPE signal was nonexponential with a first time constant below 10 fs, a dip in the 50 fs to 100 fs range, and a tail lasting for picoseconds. It was attributed to the release of the electrons from the surface and their escape into the bulk of the semiconductor.

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“…57 The surface recession velocity via the electronic ablation mechanism u e ͑t͒ will be introduced below in Sec. III D.…”

Section: ͑17͒mentioning

confidence: 99%

Insight into electronic mechanisms of nanosecond-laser ablation of silicon

Marine

Bulgakova

Patrone

et al. 2008

Journal of Applied Physics

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To cite this version:Wladimir Marine, N.M. Bulgakova, Lionel Patrone, Igor Ozerov. Insight into electronic mechanisms of nanosecond-laser ablation of silicon. We present experimental and theoretical studies of nanosecond ArF excimer laser desorption and ablation of silicon with insight into material removal mechanisms. The experimental studies involve a comprehensive analysis of the laser-induced plume dynamics and measurements of the charge gained by the target during irradiation time. At low laser fluences, well below the melting threshold, high-energy ions with a narrow energy distribution are observed. When the fluence is increased, a thermal component of the plume is formed superimposing on the nonthermal ions, which are still abundant. The origin of these ions is discussed on the basis of two modeling approaches, thermal and electronic, and we analyze the dynamics of silicon target excitation, heating, melting, and ablation. An electronic model is developed that provides insight into the charge-carrier transport in the target. We demonstrate that, contrary to a commonly accepted opinion, a complete thermalization between the electron and lattice subsystems is not reached during the nanosecond-laser pulse action. Moreover, the charging effects can retard the melting process and have an effect on the overall target behavior and laser-induced plume dynamics.

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Ultrafast Carrier Dynamics in Silicon: A Two-Color Transient Reflection Grating Study on a(111)Surface

Cited by 189 publications

References 20 publications

Reduction of carrier mobility in semiconductors caused by charge-charge interactions

Reduction of carrier mobility in semiconductors caused by charge-charge interactions

Escape dynamics of photoexcited electrons at catechol:TiO2(110)

Insight into electronic mechanisms of nanosecond-laser ablation of silicon

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