title: Efficiency improvement in the cantilever photothermal excitation method using a photothermal conversion layer.
abstract: Photothermal excitation is a cantilever excitation method that enables stable and accurate operation for dynamic-mode AFM measurements. However, the low excitation efficiency of the method has often limited its application in practical studies. In this study, we propose a method for improving the photothermal excitation efficiency by coating cantilever backside surface near its fixed end with colloidal graphite as a photothermal conversion (PTC) layer. The excitation efficiency for a standard cantilever of PPP-NCHAuD with a spring constant of ≈40 N/m and a relatively stiff cantilever of AC55 with a spring constant of ≈140 N/m were improved by 6.1 times and 2.5 times, respectively, by coating with a PTC layer. We experimentally demonstrate high stability of the PTC layer in liquid by AFM imaging of a mica surface with atomic resolution in phosphate buffer saline solution for more than 2 h without any indication of possible contamination from the coating. The proposed method, using a PTC layer made of colloidal graphite, greatly enhances photothermal excitation efficiency even for a relatively stiff cantilever in liquid.
authors.affiliation: Division of Electrical Engineering and Computer Science, Kanazawa University, Kanazawa, Japan.
authors.forename: Natsumi
authors.initials: N
authors.lastname: Inada
authors.affiliation: Division of Electrical Engineering and Computer Science, Kanazawa University, Kanazawa, Japan; Bio-AFM Frontier Research Center, Kanazawa University, Kanazawa, Japan; PRESTO, JST, Kawaguchi, Japan.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Asakawa
authors.affiliation: Division of Electrical Engineering and Computer Science, Kanazawa University, Kanazawa, Japan.
authors.forename: Taiki
authors.initials: T
authors.lastname: Kobayashi
authors.affiliation: Division of Electrical Engineering and Computer Science, Kanazawa University, Kanazawa, Japan; Bio-AFM Frontier Research Center, Kanazawa University, Kanazawa, Japan; ACT-C, JST, Kawaguchi, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Fukuma
keywords: atomic force microscopy; cantilever excitation; dynamic mode; photothermal conversion; photothermal excitation