AFM Observation of Self-Assembled Monolayer Films on GaAs (110)

Ohno, Hajime; Motomatsu, Makoto; Mizutani, Wataru; Tokumoto, Hiroshi

doi:10.1143/jjap.34.1381

Cited by 41 publications

(32 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[43] Most passivation strategies found in the literature employ inorganic or organic thiols, where sulfur is intended to bind covalently to the GaAs surface, but the stability of the adsorbed monolayers is often limited, in part due to their defective structure. [18,44] Our observations on self-assembled monolayers (SAMs) of ODT and MHDA are in accordance with earlier findings. [15,16,18,37] The ellipsometrically obtained thicknesses of 1.5 nm point to a tilted arrangement of the alkyl chains with respect to the surface normal, as has been previously reported.…”

Section: Discussionsupporting

confidence: 92%

“…[18,44] Our observations on self-assembled monolayers (SAMs) of ODT and MHDA are in accordance with earlier findings. [15,16,18,37] The ellipsometrically obtained thicknesses of 1.5 nm point to a tilted arrangement of the alkyl chains with respect to the surface normal, as has been previously reported. [37,45] Further, the surface topography after SAM formation was confirmed to have an island-like character for both compounds.…”

Section: Discussionsupporting

confidence: 92%

“…[37,45] Further, the surface topography after SAM formation was confirmed to have an island-like character for both compounds. [16,18] The wetting behavior of these surfaces by deionized water further points to their poor quality. Although the increase of the advancing contact angle after thiol adsorption formation corresponds to the successful deposition of a layer of hydrophobic alkyl chains on GaAs, the measured values deviate from those of the same SAMs on gold surfaces, i.e., 97 instead of 109±112 for ODT, and 81 instead of 60±65 for MHDA.…”

Section: Discussionmentioning

confidence: 99%

“…[15] Also, as on gold, alkane thiols were used to introduce surface functionalities present at the x-end of the mercaptoalkyl chain, [12,16] such as the carboxy group in 16-mercaptohexadecanoic acid (MHDA). [12,16] However, whereas oxide regrowth is remarkably inhibited at the thiol/GaAs interface, [17] surface coverage is often incomplete, [16,18] and the monolayer films are gradually disrupted over the course of hours to days unless they are stored in an inert atmosphere. [15] To improve thiol binding to the GaAs surface, in-situ etching methods have been introduced to avoid oxide regrowth on freshly etched substrates, [19,20] which would otherwise occur immediately upon exposure to air.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Corrosion Protection and Long-Term Chemical Functionalization of Gallium Arsenide in an Aqueous Environment

et al. 2002

View full text Add to dashboard Cite

The chemical instability of the gallium arsenide surface poses a serious limitation to its use under ambient conditions, such as in air or aqueous solution. It is shown that both bare GaAs and GaAs coated with self‐assembled monolayers of organic alkanethiols are continuously etched in aqueous environments, which limits their use as biosensor devices in physiological environments. A corrosion protection material having long‐term stability (“chemical passivation”) and biocompatibility (“biological passivation”) with the GaAs surface was found to be interfacial layers of polymerized organic mercaptosilanes a few tens of nanometers thick. The mercaptosilanes not only provided a nearly perfect corrosion protection of GaAs in water, but they also have the potential to introduce chemical groups that allow easy, further surface functionalization. Characterization of the interfacial polymer layer and its protective role was done by atomic force microscopy (AFM), ellipsometry, contact angle measurements, and atomic absorption spectroscopy (AAS). The interfacial polymer layers fully suppressed the release of arsenic into the electrolyte buffer and also provided an adhesion‐promoting interface, which allowed the cultivation of electrically excitable cells, normal rat kidney (NRK) fibroblasts, on GaAs. The electrical performance of GaAs and GaAs/InGaAs heterostructures in water was monitored via cyclic voltammetry and the IU characteristics of field‐effect channels. GaAs was significantly stabilized by the insulating polymeric surface coatings, even under moderate electrochemical loads. These findings are promising for, e.g., the implementation of GaAs technology in future cell–semiconductor hybrids.

show abstract

Section: Discussionsupporting

confidence: 92%

Section: Discussionsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Corrosion Protection and Long-Term Chemical Functionalization of Gallium Arsenide in an Aqueous Environment

et al. 2002

View full text Add to dashboard Cite

show abstract

“…We can eliminate the latter contribution and estimate the film conductance by analyzing the dependence on the separation of the electrodes. An Ag film with a thickness of about 500 nm was evaporated on the cleaned surface of a semi-insulator GaAs wafer and the SAM film was made by cleaving the GaAs with the Ag film in a solution of pyridine thiol and butane thiol [14,15]. In this case, we detected current up to 10 nA adjacent to the Ag region using AFM at sample bias voltages of +2 or 3 V between the tip and the Ag electrode.…”

Section: Resultsmentioning

confidence: 99%

Intermolecular electrical conductance in self-assembled monolayers

Inoue¹,

Mizutani²,

Ishida³

et al. 1998

Applied Physics A: Materials Science & Processing

View full text Add to dashboard Cite

Intermolecular interaction was investigated by measuring the properties of self-assembled monolayers (SAMs) in the lateral direction. We formed SAMs of octadecyltrichlorosilane (OTS) and phenethyltrichlorosilane with Ag-or Au-patterned electrodes on mica surfaces and measured the conductance under various bias voltages. Using an atomic force microscope with a conductive cantilever, we could not detect current through the SAMs in the vicinity of the electrodes about 85 nm from the edge. The resistivity of the OTS film measured using the substrates with interdigitated (comb) electrodes was strongly dependent on the humidity. From the result in a dry N 2 atmosphere, the resistivity of a SAM of OTS in a lateral direction was estimated to be ∼ 9 × 10 10 Ω cm.Self-assembled monolayers (SAMs) are one of the promising candidates for sensors, ultra-thin passivating and insulating layers, resists for nanometer-scale lithography, and new devices, because their properties can be controlled by changing the species of constituent molecules. So far, a great number of studies have been made on the structure, formation process, physical properties, and so on. The study of the electrical properties has just started from both experimental and theoretical points of view. Most studies have been concerned with the electrical conduction along the molecular axis [1-4], but there have been few studies on the electrical conduction in the lateral direction, parallel to the surface of SAMs. Possible ways to measure the conductivity of SAMs are to make films on an insulating substrate with patterned electrodes (Fig. 1a), to form electrodes on the films (Fig. 1b), and to form films on the flat substrate with buried conductive regions (Figs. 1c,d).In this study, we formed SAMs on the metal-patterned substrates as shown in Fig. 1a and measured the electrical conductivity of SAMs in the lateral direction using atomic force microscopy (AFM) with a conductive cantilever as a counterelectrode. Generally, it is not easy to form SAMs on the patterned substrates, because their formation is quite sensitive to * Permanent address: Electrotechnical Laboratory, Tsukuba, Ibaraki 305. the nature of the substrate surfaces, e.g. its chemical properties, contaminations, and roughness. However, with a careful cleaning process, residuals in the process for forming electrodes were removed thoroughly, and we could form SAMs of the same quality as those on the pristine surface. Adding the electrode after the SAM formation (Fig. 1b) might cause some damage to the film. We also carried out macroscopic measurements of the conductivity of SAMs under controlled S A M electrode substrate (a) (b) conductive region (c) (d) conductive layer Fig. 1a-d. Schematic drawings for possible structures of SAMs on substrates with electrodes. a A SAM on the electrode-patterned substrate. b Electrode pattern on the substrate coated by a SAM c, d SAM on the flat substrate with a buried conductive region or layer. Substrates are insulative

show abstract

Organic Molecular Films

Yamada¹

2002

Noncontact Atomic Force Microscopy

View full text Add to dashboard Cite

AFM Observation of Self-Assembled Monolayer Films on GaAs (110)

Cited by 41 publications

References 0 publications

Corrosion Protection and Long-Term Chemical Functionalization of Gallium Arsenide in an Aqueous Environment

Corrosion Protection and Long-Term Chemical Functionalization of Gallium Arsenide in an Aqueous Environment

Intermolecular electrical conductance in self-assembled monolayers

Organic Molecular Films

Contact Info

Product

Resources

About