Effect of the chemical composition on the work function of gold substrates modified by binary self-assembled monolayers

Abstract

This study demonstrated that the work function (Φ) of Au substrates can be fine-tuned by using series ratios of binary self-assembled monolayers (SAMs). By using pure amine- and carboxylic acid-bearing alkanethiol SAM on gold substrates, Φ of Au changed from 5.10 to 5.16 and 5.83, respectively, as determined by ultra-violet photoelectron spectrometry (UPS). The shift in Φ due to the use of different functional groups was rationalized by considering the dipole moments of the molecules anchored on the Au surface. A series of binary SAMs were fabricated by mixing carboxylic acid- and amine-terminated alkanethiols in the deposition solution. By mixing these functional groups in SAMs, a linear correlation between Φ with respect to chemical composition (hence the effective dipole moment on the Au surface) was observed. It was found that arbitrary Φ between extremes (5.16 and 5.83) controlled by respective functional groups can be obtained by changing the chemical composition of SAMs. The Scanning Kelvin Probe (SKP) was also used to measure the contact potential difference (CPD) between SAMs and referencing Au on a patterned substrate prepared by photo-lithography. It was found that the CPD of SAMs with different chemical compositions correlates to their Φ. However, the magnitude of the CPD was smaller than the difference in Φ measured by UPS that was possibly due to the adsorption of contaminants in air.

Electrical characterization of H2S adsorption on hexagonal WO3 nanowire at room temperature

“…In our Au/WO 3 /Au devices, WO 3 is an n-type semiconductor with electron affinity less than the work function of electrode Au, [30][31][32] and there should be Schottky barrier forming at the Au/WO 3 interface in the ideal case without surface states and other anomalies (Fig. 6).…”

Modulating the Electronic Properties of Au–MoS2 Interfaces Using Functionalized Self-Assembled Monolayers

“…Thus, the interaction between the Au substrate and deposited MoS 2 is likely due to charge transfer mediated by the net dipole moment of the SAMs. There are two contributions to the dipole moment of the alkanethiolate SAM: the bond dipole because of the Au–S interface and the dipole moments of the molecules within the SAM. , The orientation and magnitude of this SAM dipole is therefore dependent on the chemical composition of the SAM, including its alkyl chain length and functional groups, ,, and has been demonstrated to increase and decrease the work function of gold. ,, Further, the surface dipole moments of functionalized SAMs have been employed to control the charge channel density of organic thin-film transistors as well as the properties of superhydrophobic surfaces. , …”

“…19,34 The orientation and magnitude of this SAM dipole is therefore dependent on the chemical composition of the SAM, including its alkyl chain length and functional groups, 19,34,35 and has been demonstrated to increase and decrease the work function of gold. 21,34,36 Further, the surface dipole moments of functionalized SAMs have been employed to control the charge channel density of organic thin-film transistors 18 as well as the properties of superhydrophobic surfaces. 34,37 To investigate the effect of the SAM substrate adsorbed on gold on the MoS 2 deposit, we obtained valence band (VB) XPS data.…”

Photovoltaic Effect of a Ferroelectric-Luminescent Heterostructure under Infrared Light Illumination

“…To explain these experimental results, energy band diagrams for Au/BFO/ITO in different situations should be examined (Figures 5b -5d). The work functions of Au and ITO we use here are about 5.1 eV and 4.5 eV, respectively [48][49] , the electron affinity of BFO used is about 3.3 eV 50 , the bandgap of BFO in this report is 2.6 eV, and we suppose that the BFO Fermi level is around the middle of the bandgap. The work function of the BFO thin film is therefore about 4.6 eV.…”