Submolecular-scale investigations on metal-phthalocyanine monolayers by frequency modulation atomic force microscopy

金沢大学フロンティアサイエンス機構Copper-phthalocyanine (CuPc) monolayers and cobalt-phthalocyanine monolayers deposited on Au(111) surfaces were investigated by frequency modulation atomic force microscopy (FM-AFM). Submolecular-resolution topographic images were successfully obtained for both samples. Despite the similar molecular geometry of the two molecules, they showed clearly different contrasts in the topographic images. The origin of the contrast is discussed in terms of the relationship of the molecular orbitals and the chemical interaction between the tip and the molecules. In addition, a molecular-resolution surface potential (SP) image was obtained on CuPc monolayers using Kelvin probe force microscopy (KFM) utilizing FM-AFM. The molecular-scale SP contrast was explained by the electric dipole moment at the organic/metal interface. This result suggested the possibility of the detection of the single molecular dipole moment by KFM. © 2010 American Institute of Physics

Molecular resolution imaging of protein molecules in liquid using frequency modulation atomic force microscopy

金沢大学フロンティアサイエンス機構We demonstrated molecular resolution imaging of biological samples such as bacteriorhodopsin protein molecules in purple membrane and isolated chaperonin (GroEL) protein molecules, both adsorbed on mica using frequency modulation atomic force microscope (FM-AFM) in liquid. We also showed that the frequency noise of FM-AFM in liquid can be greatly reduced by the reduction of the noise-equivalent deflection of an optical beam deflection sensor. © 2009 The Japan Society of Applied Physics

Near-field light detection by conservative and dissipative force modulation methods using a piezoelectric cantilever

金沢大学フロンティアサイエンス機構We demonstrated near-field light detection by dynamic force microscope using a self-sensing piezoelectric cantilever having a lead zirconate titanate thin film layer. The cantilever tip was brought close to a glass plate with a patterned chromium film on a right angle prism. The backside of the prism was irradiated by an intensity modulated laser light to create an evanescent field at the glass surface. We obtained near-field optical images of the patterned glass by detecting the frequency shift modulation or the amplitude modulation induced by the near-field light while the tip-sample distance was regulated by the frequency modulation method in ambient condition. © 2010 American Institute of Physics

Surface potential measurements by the dissipative force modulation method

In this study, we propose a novel surface property measurement technique using noncontact atomic force microscopy (NC-AFM), which is referred to as the “dissipative force modulation (DM) method.” NC-AFM-based surface property measurements have mostly utilized conservative tip-sample interaction forces, which induce a frequency shift of cantilever resonance without dissipating cantilever vibration energy. In the DM method, local surface properties are measured by detecting a modulated dissipative tip–sample interaction force which dissipates cantilever vibration energy and hence induces an amplitude variation in cantilever vibration. Since the force sensitivity to dissipative interactions obtained in a typical NC-AFM setup is much higher than that to conservative ones, the DM method can improve the sensitivities of conventional NC-AFM-based techniques that utilize conservative interactions. Combining this method with Kelvin-probe force microscopy, we present the first quantitative surface potentialmeasurement through dissipative tip–sample interactions

Molecular-scale noncontact atomic force microscopy contrasts in topography and energy dissipation on c(4x2) superlattice structures of alkanethiol self-assembled monolayers

Alkanethiol self-assembledmonolayers formed on Au(111) surfaces were investigated by noncontact atomic force microscopy (NC-AFM). Dodecanethiol monolayers prepared at 78 °C were imaged by NC-AFM, which revealed that the film is composed predominantly of two different phases of c(4×2)superlattice structures. The obtained molecular-scale NC-AFM contrasts are discussed in comparison with previously reported scanning tunneling microscopy images. We found that the energy dissipation image exhibits a clear difference in its molecular-scale contrast between the two phases. Possible origins of the difference are discussed in relation to the fluctuation and/or stability of the packing structures

Submolecular-scale Investigations on metal-phthalocyanine monolayers by frequency modulation atomic force microscopy

Copper-phthalocyanine (CuPc) monolayers and cobalt-phthalocyanine monolayers deposited on Au(111) surfaces were investigated by frequency modulation atomic force microscopy (FM-AFM). Submolecular-resolution topographic images were successfully obtained for both samples. Despite the similar molecular geometry of the two molecules, they showed clearly different contrasts in the topographic images. The origin of the contrast is discussed in terms of the relationship of the molecular orbitals and the chemical interaction between the tip and the molecules. In addition, a molecular-resolution surface potential (SP) image was obtained on CuPc monolayers using Kelvin probe force microscopy (KFM) utilizing FM-AFM. The molecular-scale SP contrast was explained by the electric dipole moment at the organic/metal interface. This result suggested the possibility of the detection of the single molecular dipole moment by KFM

Near-field light detection by conservative and dissipative force modulation methods using a piezoelectric cantilever

We demonstrated near-field light detection by dynamic force microscope using a self-sensing piezoelectric cantilever having a lead zirconate titanate thin film layer. The cantilever tip was brought close to a glass plate with a patterned chromium film on a right angle prism. The backside of the prism was irradiated by an intensity modulated laser light to create an evanescent field at the glass surface. We obtained near-field optical images of the patterned glass by detecting the frequency shift modulation or the amplitude modulation induced by the near-field light while the tip-sample distance was regulated by the frequency modulation method in ambient condition