STM investigations with atomic resolution on the (2 × 1) monohydride natural doped diamond (100) surface

Nützenadel, Christoph; Küttel, O. M.; Diederich, L.; Maillard-Schaller, E.; Gröning, Oliver; Schlapbach, L.

doi:10.1016/s0039-6028(96)01120-x

Cited by 27 publications

(13 citation statements)

References 25 publications

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“…Further H-plasma treatment leads to an additional roughness enhancement by another factor of ten up to 40 nm rms , although only a layer of about 110 nm is removed by the plasma exposure. The discrepancy between our experiments and those reported in [4,5] might well be due to some different experimental conditions, such as plasma density and/or exposure time. On the other hand, our results are corroborated by Lee and Badzian [8], who have studied the morphology of etched substrates and homoepitaxial diamond films in relation to the miscut angles of the substrates.…”

Section: Discussioncontrasting

confidence: 99%

“…Kühnle and Weis have developed a chemomechanical polishing procedure that reduces the roughness of diamond {100} to less than 100 pm rms [3]. Others have used hydrogen-plasma etching to reduce the surface roughness, resulting in large atomically flat terraces [4,5]. On the other hand, etching of the diamond(100) with atomic hydrogen at an elevated substrate temperature has led to {111} faceting of the surface, which has been interpreted as anisotropic etching of the diamond by the thermal hydrogen atoms [14].…”

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Roughness transitions of diamond(100) induced by hydrogen-plasma treatment

Koslowski

Strobel

Wenig

et al. 1998

Applied Physics A: Materials Science & Processing

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To investigate the influence of hydrogen-plasma treatment on diamond(100) surfaces, heavily boron (B)-doped HPHT diamond crystals were mechanically and chemo-mechanically polished, and exposed to a microwaveassisted hydrogen plasma on a time scale of several minutes. The resulting surface morphology was analyzed on macroscopic scales by stylus profilometry (PFM) and on microscopic scales by STM and AFM. The polished samples have a roughness of typically 100 pm rms (PFM), with no obvious anisotropic structures at the surface. After exposure of the B-doped diamond(100) to the H-plasma, the roughness increases dramatically, and pronounced anisotropic structures appear, these being closely aligned with the crystallographic axis' and planes. An exposure for 3 minutes to the plasma leads to an increase of the roughness to 2-4 nm rms (STM), and a 'brick-wall' pattern appears, formed by weak cusps running along 110 . Very frequently, the cusps are replaced by 'negative' pyramids that are bordered by {11X} facets. After an exposure of an additional 5 minutes, the surface roughness of the B-doped samples increases further to 20-40 nm rms (STM), and frequently exhibits a regular pattern with structures at a characteristic length scale of about 100 nm. Those structures are aligned approximately with 110 and they are faceted with faces of approximately {XX1}. These results will be discussed in terms of strain relaxation, similar to the surface roughening observed on SiGe/Si and anisotropic etching.Many studies have been undertaken on CVD diamond films, towards applications that utilize the outstanding properties of diamond. So far, unmet demands are being put on the quality of those films, especially if one is aiming at utilizing the diamond films for semiconductor applications. Homoepitaxially grown single-crystalline diamond films are closest to meeting such requirements. Even though, nowadays, many research groups are able to grow high-quality diamond films homoepitaxially, various questions related to, for example, the nucleation and growth mechanism, the role of hydrogen in the bulk and at the surface, and the evolution of the morphology upon growth and etching of the diamond remain unanswered.The surface morphology of diamond substrates and films has been investigated by several groups. Since the substrate morphology is at least partly transferred to the film (see, e.g., [1]) and, for example, the resulting step density of a homoepitaxially grown film might influence its electronic properties at the surface [2], an optimized substrate preparation is required. Kühnle and Weis have developed a chemomechanical polishing procedure that reduces the roughness of diamond {100} to less than 100 pm rms [3]. Others have used hydrogen-plasma etching to reduce the surface roughness, resulting in large atomically flat terraces [4,5]. On the other hand, etching of the diamond(100) with atomic hydrogen at an elevated substrate temperature has led to {111} faceting of the surface, which has been interpreted as anisotropic etching of th...

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Section: Discussioncontrasting

confidence: 99%

mentioning

confidence: 99%

Roughness transitions of diamond(100) induced by hydrogen-plasma treatment

Koslowski

Strobel

Wenig

et al. 1998

Applied Physics A: Materials Science & Processing

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“…If a diamond surface shows NEA, then x is negasurface presents a (2×1) reconstruction, as shown by the LEED patterns [21,38,40] and by the tive and hence electrons thermalizing to the CBM are emitted very easily into the vacuum. They atomic resolution STM images [41] ( Fig. 2, note that the two (2×1) domains rotated by 90°with appear in the He I spectra as a sharp, highintensity peak at low kinetic energies, and the respect to each other are clearly visible).…”

Section: Sample Description and Preparationmentioning

confidence: 97%

Electron affinity and work function of differently oriented and doped diamond surfaces determined by photoelectron spectroscopy

et al. 1998

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We investigate band bending, electron affinity and work function of differently terminated, doped and oriented diamond surfaces by X-ray and ultraviolet photoelectron spectroscopy ( XPS and UPS ). The diamond surfaces were polished by a hydrogen plasma treatment and present a mean roughness below 10 Å . The hydrogen-terminated diamond surfaces have negative electron affinity (NEA), whereas the hydrogen-free surfaces present positive electron affinity (PEA). The NEA peak is only observed for the borondoped diamond (100)-(2×1):H surface, whereas it is not visible for the nitrogen-doped diamond (100)-(2×1):H surface due to strong upward band bending. For the boron-doped diamond (111)-(1×1):H surface, the NEA peak is also absent due to the conservation of the parallel wavevector component (k d ) in photoemission. Electron emission from energy levels below the conduction band minimum (CBM ) up to the vacuum level E vac allowed the electron affinity to be measured quantitatively for PEA as well as for NEA. The emission from populated surface states forms a shoulder or a peak at lower kinetic energies, depending on the NEA behavior and additionally shows a dispersion behavior. The low boron-doped diamond (100)-(2×1):H surface presents a highintensity NEA peak with a FWHM of 250 meV. Its cut-off is situated at a kinetic energy of 4.9 eV, whereas the upper limit of the vacuum level is situated at 3.9 eV, resulting in a NEA of at least −1.0 eV and a maximum work function of 3.9 eV. The high-borondoped diamond (100) surface behaves similarly, showing that the NEA peak is present due to the downward band bending independent of the boron concentration. The nitrogen-doped (100)-(2×1):H surface shows a low NEA of −0.2 eV but no NEA peak due to the strong upward band bending. The (111)-(1×1):H surface does not show a NEA peak due to the k d conservation in photoemission; E vac is situated at 4.2 eV or below, resulting in a NEA of at least −0.9 eV and a maximum work function of 4.2 eV. The high-intensity NEA peak of boron-doped diamond seems to be due to the downward band bending together with the reduced work function because of hydrogen termination. Upon hydrogen desorption at higher annealing temperatures, the work function increases, and NEA disappears. For the nitrogen-doped diamond (100) surface, the work function behaves similarly, but the observation of a NEA peak is absent because of the surface barrier formed by the high upward band bending.

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“…In this work we present an investigation of the surface presents a (2×1) reconstruction as shown by the low energy electron diffraction (LEED) NEA peak as well as quantitative NEA values of the different terminated and oriented diamond pattern [4,17] and by the atomic resolution scanning tunneling microscopy (STM ) images [6,20]. surfaces.…”

Section: Introductionmentioning

confidence: 99%

NEA peak of the differently terminated and oriented diamond surfaces

et al. 1999

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The negative electron affinity (NEA) peak of differently terminated and oriented diamond surfaces is investigated by means of ultraviolet photoemission spectroscopy. Electron emission measurements in the range below the conduction band minimum (CBM ) up to the vacuum level E vac permit the quantitative calculation of the upper limit of the NEA value. The inelastic scattering at the surface to the vacuum interface and the emission of electrons from the unoccupied surface states, situated in the band gap, are the mechanisms responsible for explaining this below CBM emission. All the H-terminated diamond surfaces present NEA. However, the characteristic NEA peak observed in the spectra is only detected for the (100)-(2×1):H surface and to a lesser extent for the (110)-(1×1):H surface, while it is absent for the (111)-(1×1):H surface because of the k || -conservation in the photoemission process.

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STM investigations with atomic resolution on the (2 × 1) monohydride natural doped diamond (100) surface

Cited by 27 publications

References 25 publications

Roughness transitions of diamond(100) induced by hydrogen-plasma treatment

Roughness transitions of diamond(100) induced by hydrogen-plasma treatment

Electron affinity and work function of differently oriented and doped diamond surfaces determined by photoelectron spectroscopy

NEA peak of the differently terminated and oriented diamond surfaces

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