A Near Edge X-ray Absorption Fine Structure Spectroscopy and X-ray Photoelectron Spectroscopy Study of the Film Properties of Self-Assembled Monolayers of Organosilanes on Oxidized Si(100)

Bierbaum, K.; Kinzler, M.; Wöll, Ch.; Grunze, M.; Hähner, Georg; Heid, Stephan; Effenberger, Franz

doi:10.1021/la00002a025

Cited by 242 publications

(278 citation statements)

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“…2͑b͒. This behavior, previously reported for silicon dioxide surfaces by Bierbaum et al, 6 was also observed for APTESmodified GaN. Quantitative analysis of the evolution of the Al 2p, Ga 3d, Ga 2p 3/2 , C 1s, and O 1s core-level peaks ͑not shown͒ indicates an ODTMS-layer thickness of 1.7± 0.4 nm ͑1.8± 0.4 nm͒ for GaN ͑AlN͒.…”

supporting

confidence: 77%

“…3,4 Covalent grafting of self-assembled monolayers ͑SAMs͒ of organosilanes on oxidized silicon surfaces [5][6][7] is widely used as the first step of surface functionalization with biomolecules for electronic detection of enzyme activity and DNA hybridization with Si-based field effect transistors. 8,9 In contrast, the surface chemistry on AlGaN alloys has not yet been studied in great detail.…”

mentioning

confidence: 99%

“…[5][6][7] Therefore, the substrates were immersed in H 2 SO 4 :H 2 O 2 ͑3:1͒ solution for 20 min, rinsed with deionized water ͑18 M⍀ cm, Millipore͒ and dried under nitrogen flux prior to silanization. In addition to the activation of surface hydroxyl groups, this treatment leads to the formation of a thin oxide layer on GaN which has been proven by XPS.…”

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Chemical functionalization of GaN and AlN surfaces

Baur

Steinhoff

Hernando

et al. 2005

Applied Physics Letters

125

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The covalent functionalization of GaN and AlN surfaces with organosilanes is demonstrated. Both octadecyltrimethoxysilane and aminopropyltriethoxysilane form self-assembled monolayers on hydroxylated GaN and AlN surfaces, confirmed by x-ray photoelectron spectroscopy and atomic force microscopy. The monolayer thickness on GaN was determined to 2.5± 0.2 nm by x-ray reflectivity. Temperature-programmed desorption measurements reveal a desorption enthalpy of 240 kJ/ mol. The application of these devices for electronic detection of specific biomolecular processes is a promising approach for novel biosensors based on molecular recognition, such as specific antibody detection or label-free detection of deoxyribonucleic acid ͑DNA͒ hybridization. For this purpose, the covalent attachment of specific molecules with controlled structural order and composition on group III-nitride devices is a basic requirement.Covalent coupling of biomolecules to oxidized and hydrogen-terminated silicon surfaces has been investigated in numerous works during recent decades. 3,4 Covalent grafting of self-assembled monolayers ͑SAMs͒ of organosilanes on oxidized silicon surfaces 5-7 is widely used as the first step of surface functionalization with biomolecules for electronic detection of enzyme activity and DNA hybridization with Si-based field effect transistors. 8,9 In contrast, the surface chemistry on AlGaN alloys has not yet been studied in great detail. Pioneering work has been carried out by Bermudez, 10,11 who has analyzed the adsorption of different organic molecules, such as anilines or octanethiols on GaN surfaces, from the gas phase. In a recent publication Kang et al. 12 have reported the electrical detection of immobilized proteins on AlGaN / GaN transistors, modified with aminopropyltriethoxysilane ͑APTES͒ molecules in a liquid phase reaction. However, the covalent immobilization of molecules was not proven.In this letter, we report the covalent attachment of SAMs of octadecyltrimethoxysilane ͑ODTMS͒ and APTES on hydroxylated GaN and AlN surfaces. Complementary analysis by x-ray photoelectron spectroscopy ͑XPS͒, atomic force microscopy ͑AFM͒, and temperature-programmed desorption mass spectrometry proves covalent coupling of the SAMs to the surface. Immobilization of single-stranded 20-mer oligonucleotides on APTES-modified nitride surfaces and hybridization is demonstrated by fluorescence microscopy.GaN and AlN layers with a thickness of 2 m were grown by metalorganic chemical vapor deposition ͑MOCVD͒ on c-plane sapphire substrates. AFM over a scan area of 4 m 2 revealed a root-mean-square surface roughness of 0.2 nm for GaN and 0.3 nm for AlN, respectively.The presence of hydroxyl groups on the hydrophilic surface is an essential requirement for the silanization process. 5-7 Therefore, the substrates were immersed in H 2 SO 4 :H 2 O 2 ͑3:1͒ solution for 20 min, rinsed with deionized water ͑18 M⍀ cm, Millipore͒ and dried under nitrogen flux prior to silanization. In addition to the activation of surface hydroxyl groups, this...

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supporting

confidence: 77%

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confidence: 99%

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Chemical functionalization of GaN and AlN surfaces

Baur

Steinhoff

Hernando

et al. 2005

Applied Physics Letters

125

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“…Good quality SAMs result from a low siloxane polymerization rate in solution relative to SAM formation on the substrate. Trialkoxysilanes, with their relatively slow hydrolysis rates in solution, are excellent reagents for high quality SAM formation on silicon surfaces, exhibiting little sensitivity to the amount of trace water content in solution (35,36).…”

Section: Sam Preparation and Characterizationmentioning

confidence: 99%

Protein Adhesion on SAM Coated Semiconductor Wafers: Hydrophobic versus Hydrophilic Surfaces

Follstaedt¹,

Cheung²,

Gourley³

et al. 2000

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The interface of biology and semiconductor materials has become an important topic of interest as researchers are merging living organisms with microelectromechanical systems (MEMS) in the pursuit of new microfabricated biomedical devices. Biological cells interface with the semiconductor surface through a host of interactions that are mediated by protein adhesion and film formation. To better understand this interface, we have conducted protein adsorption studies of a model system using bovine serum albumin (BSA) and compared it to the adsorption from a complex protein mixture of cell growth serum on uncoated and self-assembled monolayer (SAM) coated silicon wafers. Several characterization techniques -AFM, ellipsometry, water contact angle, and fluorescence microscopy -were used to evaluate the protein-adsorbed layer. An uncoated silicon surface was most attractive to proteins, forming a 70 Å thick film from a solution of BSA at a concentration comparable to that in cell growth serum. Coating with the hydrophobic octadecyltrimethoxysilane (OTMS) SAM reduced protein adhesion by ~15%. In contrast, a hydrophilic N-(triethoxysilylpropyl)-O-polyethyleneoxide urethane (TESP) SAM inhibited protein adhesion by greater than 50%. Protein adhesion studies with cell growth sera containing complex mixtures of proteins paralleled the BSA adsorption studies, clearly identifying the TESP coated surface as a promising biocompatible coating.4

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“…Amino-terminated organic layers have been covalently attached onto silicon surface using the reaction of x-aminotrialkoxysilanes with oxidized silicon surfaces. [33][34] However, the direct use of x-aminotrialkoxysilanes resulted in disordered layers or multilayers. [33][34][35] Therefore, in this work we report another approach to prepare amino-terminated silicon surface.…”

Section: Resultsmentioning

confidence: 99%