Arai Toyoko, Koshioka Masashi, Abe Kouhei, Tomitori Masahiko, Kokawa Ryohei, Ohta Masahiro, Yamada Hirofumi, Kobayashi Kei, Oyabu Noriaki
†Natural Science and Technology, Kanazawa University, Kanazawa, Ishikawa 920-1192, Japan.
‡School of Materials Science, Japan Advanced Institute of Science and Technology, Nomi, Ishikawa 923-1292, Japan.
Langmuir. 2015 Apr 7;31(13):3876-83. doi: 10.1021/acs.langmuir.5b00087. Epub 2015 Mar 30.
An ionic KBr(001) crystal surface covered with a thin water layer was observed with a frequency modulation atomic force microscope (FM-AFM) with atomic resolution. By immersing only the tip apex of the AFM cantilever in the thin water layer, the Q-factor of the cantilever in probing the solid-liquid interface can be maintained as high as that of FM-AFM operation in air, leading to improvement of the minimum detection of a differential force determined by the noise. Two types of images with atom-resolved contrast were observed, possibly owing to the different types of ions (K(+) or Br(-)) adsorbed on the tip apex that incorporated into the hydration layers on the tip and on the sample surface. The force-distance characteristics at the solid-water interface were analyzed by taking spatial variation maps of the resonant frequency shift of the AFM cantilever with the high Q-factor. The oscillatory frequency shift-distance curves exhibited atomic site dependence. The roles of hydration and the ions on the tip and on the sample surface in the measurements were discussed.
利用具有原子分辨率的调频原子力显微镜（FM-AFM）观察了覆盖有薄水层的离子型KBr(001)晶体表面。通过仅将AFM悬臂的尖端浸入薄水层中，在探测固液界面时悬臂的品质因数可以保持与在空气中FM-AFM操作时一样高，从而提高了由噪声决定的差分力的最小检测量。观察到了两种具有原子分辨对比度的图像，这可能是由于吸附在尖端顶点的不同类型离子（K(+)或Br(-)）掺入了尖端和样品表面的水化层中。通过获取具有高品质因数的AFM悬臂共振频率偏移的空间变化图，分析了固水界面处的力-距离特性。振荡频率偏移-距离曲线表现出对原子位点的依赖性。讨论了水化以及尖端和样品表面上的离子在测量中的作用。
