Apparatus for investigating metalorganic chemical vapor deposition-grown semiconductors with ultrahigh-vacuum based techniques

Abstract

An apparatus is described here in detail for the transfer of a sample from a metalorganic chemical vapor deposition ͑MOCVD͒ reactor to an ultrahigh-vacuum ͑UHV͒ chamber without introducing any contamination. The surface of the sample does not change during transfer as is borne out by the identical reflectance difference ͑RD͒ spectrum measured first in the MOCVD reactor, i.e., in situ, and afterwards again in the UHV chamber. Making use of the earlier apparatus a semiconductor can be grown in the MOCVD reactor and can afterwards be investigated with any desired tool of surface science, in particular also those that require UHV. All the data collected in UHV can be identified with the RD spectrum measured already in the MOCVD reactor. Several examples are presented here for data collection in UHV on III-V semiconductors grown in the MOCVD reactor. They illustrate the ease and reliability of the here described apparatus for contamination-free sample transfer. Signals are presented in particular for the genuine MOCVD-grown P-rich seemingly (2 ϫ1)/(2ϫ2)InP(100) reconstructed surface that until now can only be investigated in UHV if one makes use of the sample transfer system described in this article.

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

“…38 The XPS spectrum of every commercial rutile crystal ͑Crystal GmbH, Berlin͒ showed a pronounced carbon peak that was ascribed to organic impurities. In the next step the ͑110͒ surface of the rutile crystal was cleaned and ordered by carrying out repeated cycles of Ar + ion bombardment ͑700 eV, 3 A, 10 min͒ and heating ͑875 K , 10 min͒ similar to recipes given in the literature.…”

In situ study of Ge(100) surfaces with tertiarybutylphosphine supply in vapor phase epitaxy ambient

“…The RA spectra are baseline corrected to avoid anisotropics originating from the viewport window [16]. A dedicated MOVPE-to-UHV sample transfer system [18] enabled XPS (Specs Focus 500 and Phoibos 100) and LEED (Specs ErLEED 100-A) measurements. XP spectra were analyzed using the CASAXPS commercial software [19].…”

Optical in situ monitoring of hydrogen desorption from Ge(100) surfaces

“…We correlate the RA spectrum obtained to UHV-based surface-sensitive tools such as Fourier-transform infrared (FTIR) spectroscopy, STM, and X-ray photoelectron spectroscopy (XPS) accessed by a dedicated MOVPE-to-UHV transfer system. 22 In situ RAS enables direct observations of changes on the Ge(100) surface related to hydrogen termination in any process environment, whereas LID, STM, and TPD are only applicable in UHV environment.…”

“…The origins of the RAS signals can be identified either by ab initio calculations, 19,20 modeling, 21 or by correlation of RAS signals to results from other surfacesensitive techniques. 22 Therefore, RAS signals provide control and understanding of processes on the sample surface during preparation in any process gas ambient. The potential of RAS for monitoring the temporal evolution of adsorbates was first shown for metals.…”

“…The sample transfer system enabled contamination-free access to STM (Specs Aarhus 150), XPS (Specs Focus 500 and Phoibos 100), and FTIR spectroscopy (Bruker IFS 66v/S). 22 Thermal oxide removal consisted of an annealing step at 1000 K for 20 min using 14 slpm of Pd-purified H 2 at a pressure of 100 mbar.…”