Enhanced conductance of chlorine-terminated Si(111) surfaces: Formation of a two-dimensional hole gas via chemical modification

Lopinski, Gregory P.; Eves, Brian J.; Hulko, O.; Mark, Clarisse I.; Patitsas, S. N.; Boukherroub, Rabah; Ward, T. R.

doi:10.1103/physrevb.71.125308

Cited by 25 publications

(21 citation statements)

References 23 publications

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“…Another group observed that chlorine termination of low-doped n-type Si(111) leads to an increase in conductance relative to the hydrogen terminated surface. 11 The authors attributed this enhancement to formation of a two-dimensional hole gas resulting from the strong electron-withdrawing nature of the adsorbed chlorine. On the basis of the fact that electronic properties at the semiconductor−molecule interface can be altered by changing the nature of covalent attachment, Hacker 12 examined the change in work function of the silicon surface after formation of Si−O−C, Si−C−C, and Si−S−C bonded alkyl monolayers and separated charge transfer and dipolar contributions.…”

Section: Introductionmentioning

confidence: 97%

Chemical Trends in the Work Function of Modified Si(111) Surfaces: A DFT Study

Arefi

Fagas

2014

J. Phys. Chem. C

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Using first-principles, we provide predictions for chemical trends in the work function of silicon (111) surfaces modified with various terminations. For nonpolar terminating atomic species such as F, Cl, Br, and I, the change in the work function is directly proportional to the amount of charge transferred from the surface, thus relating to the difference in electronegativity of the adsorbate and silicon atoms. The change is a monotonic function of coverage in this case, and the work function increases with increasing electronegativity. Polar species such as −TeH, −SeH, −SH, −OH, −NH 2 , −CH 3 , and −BH 2 do not follow this trend due to the interaction of their dipole with the induced electric field at the surface. In this case, the magnitude and sign of the surface dipole moment need to be considered in addition to the bond dipole to generally describe the change in work function. Compared to hydrogenated surfaces, there is slight increase in the work function of H:Si(111)-XH, where X = Te, Se, and S, whereas reduction is observed for surfaces covered with −OH, −CH 3 , and −NH 2 . Our analysis contributes to a microscopic understanding of induced changes in experimentally studied silicon surfaces.

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Section: Introductionmentioning

confidence: 97%

Chemical Trends in the Work Function of Modified Si(111) Surfaces: A DFT Study

Arefi

Fagas

2014

J. Phys. Chem. C

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“…Surface conductance measurements on Si have been reported during exposure to O 2 , Cl 2 , pyridine, dissolved redox species, and other reactive volatiles. [16][17][18][19] In situ measurements are particularly attractive in the context of ALD because each chemical step is temporally separated allowing for the correlation of chemical 20,21 and electronic 22,23 property changes with each self-limiting chemical reaction. For example, resistivity measurements of ZnO thin films were made during ALD reporting the time evolution of the conductivity during a) strand@lehigh.edu 0003-6951/2015/106(6)/061603/5/$30.00 V C 2015 AIP Publishing LLC 106, 061603-1 changes of conducting layer thickness, surface chemistry, and dopant incorporation.…”

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confidence: 99%

In situ measurement of fixed charge evolution at silicon surfaces during atomic layer deposition

Watt

Strandwitz

2015

Applied Physics Letters

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Interfacial fixed charge or interfacial dipoles are present at many semiconductor-dielectric interfaces and have important effects upon device behavior, yet the chemical origins of these electrostatic phenomena are not fully understood. We report the measurement of changes in Si channel conduction in situ during atomic layer deposition (ALD) of aluminum oxide using trimethylaluminum and water to probe changes in surface electrostatics. Current-voltage data were acquired continually before, during, and after the self-limiting chemical reactions that result in film growth. Our measurements indicated an increase in conductance on p-type samples with p+ ohmic contacts and a decrease in conductance on analogous n-type samples. Further, p+ contacted samples with n-type channels exhibited an increase in measured current and n+ contacted p-type samples exhibited a decrease in current under applied voltage. Device physics simulations, where a fixed surface charge was parameterized on the channel surface, connect the surface charge to changes in current-voltage behavior. The simulations and analogous analytical relationships for near-surface conductance were used to explain the experimental results. Specifically, the changes in current-voltage behavior can be attributed to the formation of a fixed negative charge or the modification of a surface dipole upon chemisorption of trimethylaluminum. These measurements allow for the observation of fixed charge or dipole formation during ALD and provide further insight into the electrostatic behavior at semiconductor-dielectric interfaces during film nucleation.

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“…The hydrogen atoms on the H / Si surface are well known to be desorbed with scanning tunneling microscope ͑STM͒ tip, 19 electron gun 20 or UV light, 21 while EUV or soft x ray makes no effect on the surface. 11 On the other hand, the Cl/ Si surface is affected by STM tip, 22 electron gun, 23 UV light, 24 or focused soft x ray, 12 but no change was observed upon unfocused EUV irradiation near 13.4 nm. The EUVinduced amine group modification near 13.4 nm has not been reported for amine-terminated SAMs, other well-defined molecular nanolayers, such as H / Si ͑Ref.…”

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confidence: 99%