Abstract:X-ray photoelectron spectroscopy (XPS) is used to determine the oxidation state of gold deposited from an aqueous solution of AuCl 4 -on to various oxidized surfaces of silicon. Although the observed Au4f signal decreased with the thickness of the oxide layer, the oxidation state of Au was determined as 0 for all the samples analyzed. From the angular dependence of the Si2p and Au4f signals it was determined that Au is deposited on top of the oxidized surfaces of metallic silicon. It is postulated that from an… Show more
“…The Au film is stable against repeated washing with various aqueous and organic solvents. Similar results were observed by Suzer and Dag 4 X-ray photoelectron spectra of Si and SiO 2 wafers treated with HAuCl 4 for 10 h. The XPS spectrum of the Si wafer shows significant Au deposition, whereas the XPS spectrum of the SiO 2 wafer shows no evidence of Au deposition. …”
Scanning probe lithography is a rapidly growing research field, in which atomic force microscope based "dip-pen" nanolithography (DPN) is a simple new technique for creating chemically distinct nanostructures on surfaces in a "direct-write" fashion. Previous works demonstrate the transport of alkanethiols to a gold substrate, resulting in the formation of patterned self-assembled monolayers. Here, we show that surfaceinduced reduction of metal ions combined with DPN can be used to create metallic nanostructures on Si surfaces. Au nanostructures with sub-100-nm resolution can be created routinely, showing that the DPN technique is a general method for nanofabrication.In recent years, scanning probe lithography (SPL) has attracted great attention. Many SPL techniques have been developed in the past decade based on various chemical, physical, and electrical modifications of surfaces, including mechanical scratching, 1-4 electrochemical anodization of Si surfaces, 5,6 decomposition of self-assembled monolayers, 7-10 electric field induced chemical reactions, 11,12 electrochemical reactions in solution using electrochemical scanning tunneling microscope tips, 13-18 and so forth. Several comprehensive reviews of scanning probe microscope related lithography can be found in the literature. 19-21 More recently, a new SPL technique, "dip-pen" nanolithography (DPN), 22,23 has demonstrated the ability to pattern monolayer films of thiolated organic molecules with sub-100-nm resolution on gold substrates. The technology uses the spontaneous condensation between the atomic force microscope (AFM) tip and substrate 24 to transport organic molecules from the AFM tip to the surface in the area specifically defined by the tip/surface interaction. To draw a familiar analogy, the AFM tip acts as a "pen", the organic molecules act as "ink", and the surface acts as "paper" for nanostructures to be "drawn" on. It has also been demonstrated for direct patterning of nanoscale structures in both a serial and parallel fashion. 25 This technique provides a potentially more accessible, cheaper, and versatile alternative to conventional highresolution lithographic methods such as e-beam lithography.Previous demonstrations of DPN have patterned longchain alkanethiol molecules onto gold surfaces. However, there is no reason other molecules that have a certain affinity for a specific surface could not be used for DPN. We have recently discovered that metal ions can be electrochemically reduced and deposited on surfaces to form metallic nanostructures using a modified electrochemical DPN technique. 26 Here, we report that Au(III) complexes can be used directly (without applied voltages as in the electrochemical DPN method) as "ink" for DPN on Si "paper". This is the first demonstration of an ionic substance being transported from the AFM tip and chemically reacting with the surface to form metallic nanostructures. It further demonstrates that DPN is a versatile technique that can be used to create various nanostructures in a "direct-write" fas...
“…The Au film is stable against repeated washing with various aqueous and organic solvents. Similar results were observed by Suzer and Dag 4 X-ray photoelectron spectra of Si and SiO 2 wafers treated with HAuCl 4 for 10 h. The XPS spectrum of the Si wafer shows significant Au deposition, whereas the XPS spectrum of the SiO 2 wafer shows no evidence of Au deposition. …”
Scanning probe lithography is a rapidly growing research field, in which atomic force microscope based "dip-pen" nanolithography (DPN) is a simple new technique for creating chemically distinct nanostructures on surfaces in a "direct-write" fashion. Previous works demonstrate the transport of alkanethiols to a gold substrate, resulting in the formation of patterned self-assembled monolayers. Here, we show that surfaceinduced reduction of metal ions combined with DPN can be used to create metallic nanostructures on Si surfaces. Au nanostructures with sub-100-nm resolution can be created routinely, showing that the DPN technique is a general method for nanofabrication.In recent years, scanning probe lithography (SPL) has attracted great attention. Many SPL techniques have been developed in the past decade based on various chemical, physical, and electrical modifications of surfaces, including mechanical scratching, 1-4 electrochemical anodization of Si surfaces, 5,6 decomposition of self-assembled monolayers, 7-10 electric field induced chemical reactions, 11,12 electrochemical reactions in solution using electrochemical scanning tunneling microscope tips, 13-18 and so forth. Several comprehensive reviews of scanning probe microscope related lithography can be found in the literature. 19-21 More recently, a new SPL technique, "dip-pen" nanolithography (DPN), 22,23 has demonstrated the ability to pattern monolayer films of thiolated organic molecules with sub-100-nm resolution on gold substrates. The technology uses the spontaneous condensation between the atomic force microscope (AFM) tip and substrate 24 to transport organic molecules from the AFM tip to the surface in the area specifically defined by the tip/surface interaction. To draw a familiar analogy, the AFM tip acts as a "pen", the organic molecules act as "ink", and the surface acts as "paper" for nanostructures to be "drawn" on. It has also been demonstrated for direct patterning of nanoscale structures in both a serial and parallel fashion. 25 This technique provides a potentially more accessible, cheaper, and versatile alternative to conventional highresolution lithographic methods such as e-beam lithography.Previous demonstrations of DPN have patterned longchain alkanethiol molecules onto gold surfaces. However, there is no reason other molecules that have a certain affinity for a specific surface could not be used for DPN. We have recently discovered that metal ions can be electrochemically reduced and deposited on surfaces to form metallic nanostructures using a modified electrochemical DPN technique. 26 Here, we report that Au(III) complexes can be used directly (without applied voltages as in the electrochemical DPN method) as "ink" for DPN on Si "paper". This is the first demonstration of an ionic substance being transported from the AFM tip and chemically reacting with the surface to form metallic nanostructures. It further demonstrates that DPN is a versatile technique that can be used to create various nanostructures in a "direct-write" fas...
“…Therein, the activated carbon surfaces containing basic oxygen-based functional groups displayed reductive sorption of [AuCl 4 ] - via electrochemical mechanisms, while acidic oxygen-based functional groups displayed chemical reduction mechanisms . Suzer and Dag have also reported that [AuCl 4 ] - can undergo reductive deposition to Au(0) from aqueous solution at any surface which can provide an active adsorption site . Therefore, in the present case, it is probable that the reductive sorption of [AuCl 4 ] - occurs at surface defects or impurities in the GC electrode, with protons either activating these sites or otherwise facilitating the reduction process of [AuCl 4 ] - in the IL.…”
The comparative study of the voltammetry of H[NTf2], HCl and H[AuCl4] in [C4mim][NTf2] has provided an
insight into the influence of protons on the reduction of [AuCl4]- at Au, Pt or glassy carbon (GC) electrodes,
and has allowed the identification of an unprecedented proton-induced electroless deposition of Au on relatively
inert GC surfaces. For the first time, clear evidence of the quantitative formation of [HCl2]- has been obtained
in HCl/[C4mim][NTf2] mixtures, and the electrochemical behavior of these mixtures analyzed. In particular,
a significant shift of the dissociation equilibrium toward the formation of chloride and the solvated proton
(HIL
+), following electrochemical reduction of HIL
+ has been observed in the time-scale of the experiments.
“…Examples of thin, well adhering nanoparticle films prepared via immersion of Ge(100) and metal substrates into dilute, aqueous solutions of AuCl 4 - , PdCl 4 2- , or PtCl 4 2- salts are shown in Figure . Deposition proceeds via galvanic displacement in the absence of fluoride, pH buffers, complexing agents, or external reducing agents, in contrast to earlier work. − Patterning of these particle film assemblies is essential for their subsequent incorporation into higher order architectures and devices. , 1 SEM images of (a) an Au nanoparticle film deposited spontaneously in 90 min on a Ge(100) surface from a 1 mM aqueous AuCl 4 - solution; (b) Pd and (c) Pt on a Ge(100) surface, formed from aqueous 1 mM PdCl 4 2- and PtCl 4 2- for 120 min; Pt films on (d) Zn and (e) Cu foils utilizing an aqueous 20 mM PtCl 4 2- solution for 10 s; (f) Pt on Sn foil deposited from a 20 mM PtCl 4 2- solution for 5 min.…”
Nanoparticles of Au, Pd, and Pt form spontaneously as thin, morphologically complex metallic films upon various semiconducting or metal substrates such as Ge(100), Cu, Zn, and Sn, via galvanic displacement from aqueous metal salt solutions. Patterning of these high surface area metal films into ordered structures utilizing photolithography, microcontact printing (µ-CP), and dip-pen nanolithography (DPN) is demonstrated on flat Ge(100), and (for µ-CP) on rough Zn foil.There is presently enormous interest in patterning surfaces with micro-and nanometer resolution for both fundamental investigations and technological applications.1 Recent developments, such as dip-pen nanolithography (DPN) 2 and microcontact printing (µ-CP), 1 employ a liquid-phase "ink" to pattern a solid "paper" substrate. Established inks for DPN and µ-CP include thiols, 2 DNA, 3 polymers, 4 proteins, 5,6 hexamethyldisilazane, 7 alkylsiloxanes, 8 palladium colloids, 9 sols (Al, Si, Sn oxides), 10 metal complexes, 11 and gold. 12 In this paper, we demonstrate that Au, Pd, and Pt nanoparticle films, produced through a spontaneous electroless deposition reaction, are amenable to patterning via photolithography, µ-CP, and DPN. Because many properties of the Au, Pd, and Pt nanoparticle films, including film thickness, particle size, and roughness, can be controlled, 13 Figure 1. Deposition proceeds via galvanic displacement 20 in the absence of fluoride, pH buffers, complexing agents, or external reducing agents, in contrast to earlier work. 21-30 Patterning of these particle film assemblies is essential for their subsequent incorporation into higher order architectures and devices. 31,32 The first patterning motif tested, photolithography, was carried out as outlined in Figure 2a. Approximately 0.1 mL of neat dodecene was applied to a 1 cm 2 hydride-terminated Ge(100) surface, which was subequently exposed to 254 nm UV light (9 mW cm -2 intensity) through a metal grid contact mask under an inert atmosphere. 33 The illuminated regions undergo hydrogermylation at room temperature within thirty minutes. A related functionalization approach has been shown on silicon.34 This leads to spatially defined 5-25 µm-sized domains of dodecyl and hydride. Immersion of the hydride/alkyl surface into aqueous noble metal salt solutions results in preferential deposition in the hydride areas since the alkyl monolayer functions as an effective dielectric barrier (Figure 3). The hydride surface oxidizes in-situ and subsequently dissolves in the aqueous medium. Metal salt reduction and deposition can then occur, leading to metallization between the alkylated domains. In this case, the germanium oxide dissolves in water, 35 leading to intimate electrical contact between the semiconductor bulk and the metal salts and affording a faster rate of deposition. In the case of silicon, however, this approach is not feasible because the native oxide has been shown to effectively prevent metal deposition due to its insolubility in water. 20 Attempts to use spatially define...
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