Charge trapping behavior visualization of dumbbell-shaped DSFXPY via electrical force microscopy

Abstract

The electrons and holes are injected into the sterically hindered organic semiconductor film (DSFXPY, 1,6-di(spiro[fluorene-9,90-xanthene]-2-yl)pyrene) through applying controllable biases on the conductive atomic force microscopy tip.

Injection and Retention Characterization of Trapped Charges in Electret Films by Electrostatic Force Microscopy and Kelvin Probe Force Microscopy

“…Chotsuwan and Blackstock visualized the charge trapping process of single, multicharged polyamines via KPFM, as shown in Figure a. [ 78 ] By KPFM, injection and retention processes of trapped charges in the sterically hindered organic semiconductor films (1,6‐di(spiro[fluorene‐9,90‐xanthene]‐2‐yl)pyrene) (DSFXPY), [ 42 ] spiro[fluorene‐9,7‐dibenzo[ c , h ]acridin‐5‐one] (SFDBAO), [ 43 ] and tris (8‐hydroxyquinoline) aluminum (Alq 3 ) thin films [ 44 ] were investigated. For example, the dependences of the peak potential and the area of the trapped charges for the Alq 3 film on the injection time are shown in Figure .…”

“…With the EFM/KPFM techniques, researchers have widely explored the charge trapping properties and acquired abundant experimental results. [ 16,40,42,44,46,47,55,57,60,69,70,79,87,101–103,106,112,117–121 ] Some groups have reported that charge injection is influenced by the hydrophilicity of films and the atmospheric moisture. [ 46,47,60,101–103 ] The effects of the injection time, [ 44,46,79,119 ] injection bias, [ 40,44,79,119 ] and the duration of the applied field [ 113 ] on the charge trapping processes have also been widely investigated.…”

“…The structural defects and impurities, [ 117,118 ] crystallization, [ 16,106 ] film thickness, [ 42,47,55,57,106 ] injection modes, [ 112,119 ] curvature radius and work function of the AFM tip, [ 120,121 ] and conductivity of the substrates [ 69,70,87 ] are also very important factors for the charge trapping process. Liu and coworkers investigated the effect of film thickness, crystallization, grain size, and annealing temperature on the charge trapping layer of HfO 2 and found that storage and retention capability are dependent on crystallization.…”

“…[ 24–26 ] The electrostatic force could provide such information as subsurface properties of films, [ 27–29 ] differences in the terminal group of various monolayer systems, [ 30–35 ] dopant profiles in the semiconductors, [ 36–38 ] surface compositional differences, [ 32–34 ] polarizability properties of molecules, [ 39,40 ] and charge trapping characteristics. [ 25,41–51 ]…”

“…In the past decade, EFM/KPFM has been successfully used to study the injection and retention of trapped charges in inorganic films, [ 16,25,45,46,52–57 ] polymer electrets, [ 47,58–60 ] organic small molecules, [ 42,44 ] the composition of polymer and organic semiconductors, [ 27,41,43 ] nanostructure, [ 48–51,61–78 ] double‐barrier CeO 2 /Si/CeO 2 /Si structures, [ 79 ] DNA molecules, [ 39–80 ] and thin‐film transistors. [ 81–86 ] For example, Heim et al proved that EFM is a useful technique to study the electronic properties of an organic monolayer island at the nanometer scale and found that both carriers are delocalized over the whole island in crystalline monolayer islands, while carriers stay localized at their injection point on a disordered monolayer.…”