In this paper the elastic properties of SiOx film are investigated quantitatively for local fixed point and qualitatively for overall area by atomic force acoustic microscopy （AFAM） in which the sample is vibrated a...In this paper the elastic properties of SiOx film are investigated quantitatively for local fixed point and qualitatively for overall area by atomic force acoustic microscopy （AFAM） in which the sample is vibrated at the ultrasonic frequency while the sample surface is touched and scanned with the tip contacting the sample respectively for fixed point and continuous measurements. The SiOx films on the silicon wafers are prepared by the plasma enhanced chemical vapour deposition （PECVD）, The local contact stiffness of the tip-SiOx film is calculated from the contact resonance spectrum measured with the atomic force acoustic microscopy. Using the reference approach, indentation modulus of SiOx film for fixed point is obtained. The images of cantilever amplitude are also visualized and analysed when the SiOx surface is excited at a fixed frequency. The results show that the acoustic amplitude images can reflect the elastic properties of the sample.展开更多
We investigated the orientations of interface dipole moments of individual non-planar titanyl phthalocyanine(TiOPc)molecules on Cu(111)and Cu(100)substrates using scanning tunneling microscope(STM)and noncontact atomi...We investigated the orientations of interface dipole moments of individual non-planar titanyl phthalocyanine(TiOPc)molecules on Cu(111)and Cu(100)substrates using scanning tunneling microscope(STM)and noncontact atomic force microscope(NC-AFM).The dipole moment orientations corresponding to two different configurations of individual TiOPc molecules were determined unambiguously.The correlation between the actual molecular structures and the corresponding STM topographies is proposed based on the sub-molecular resolution imaging and local contact potential difference(LCPD)measurements.Comparing with the pristine substrate,the LCPD shift due to the adsorption of non-planar molecule is dependent on the permanent molecular dipole,the charge transfer between the surface and the molecule,and the molecular configurations.This work would shed light on tailoring interfacial electronic properties and controlling local physical properties via polar molecule adsorption.展开更多
Dynamic friction occurs not only between two contact objects sliding against each other,but also between two relative sliding surfaces several nanometres apart.Many emerging micro-and nano-mechanical systems that prom...Dynamic friction occurs not only between two contact objects sliding against each other,but also between two relative sliding surfaces several nanometres apart.Many emerging micro-and nano-mechanical systems that promise new applications in sensors or information technology may suffer or benefit from noncontact friction.Herein we demonstrate the distance-dependent friction energy dissipation between the tip and the heterogeneous polymers by the bimodal atomic force microscopy(AFM)method driving the second order flexural and the first order torsional vibration simultaneously.The pull-in problem caused by the attractive force is avoided,and the friction dissipation can be imaged near the surface.The friction dissipation coefficient concept is proposed and three different contact states are determined from phase and energy dissipation curves.Image contrast is enhanced in the intermediate setpoint region.The work offers an effective method for directly detecting the friction dissipation and high resolution images,which overcomes the disadvantages of existing methods such as contact mode AFM or other contact friction and wear measuring instruments.展开更多
The properties and stability of the reported surface nanobubbles are related to the substrate used and the generation method. Here, we design a series of experiments to study the influence of the hydrophobicity of the...The properties and stability of the reported surface nanobubbles are related to the substrate used and the generation method. Here, we design a series of experiments to study the influence of the hydrophobicity of the substrate and the produc- tion method on the formation and properties of nanobubbles. We choose three different substrates, dodecyltrichlorosilane （DTS） modified silicon, octadecyltrichlorosilane （OTS） modified silicon, and highly oriented pyrolytic graphite （HOPG） as nanohubble substrates, and two methods of ethanol-water exchange and 4-℃ cold water to produce nanobubbles. It is found that using ethanol-water exchange method could produce more and larger nanobubbles than the 4-℃ cold water method. The contact angle of nanobubbles produced by ethanol-water exchange depends on the hydrophobicity of sub- strates, and decreases with the increase of the hydrophobicity of substrates. More interestingly, nanoscopic contact angle approaches the macroscopic contact angle as the hydrophobicity of substrates increases. It is believed that these results would be very useful to understand the stability of surface nanobubbles.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.50775005)
文摘In this paper the elastic properties of SiOx film are investigated quantitatively for local fixed point and qualitatively for overall area by atomic force acoustic microscopy （AFAM） in which the sample is vibrated at the ultrasonic frequency while the sample surface is touched and scanned with the tip contacting the sample respectively for fixed point and continuous measurements. The SiOx films on the silicon wafers are prepared by the plasma enhanced chemical vapour deposition （PECVD）, The local contact stiffness of the tip-SiOx film is calculated from the contact resonance spectrum measured with the atomic force acoustic microscopy. Using the reference approach, indentation modulus of SiOx film for fixed point is obtained. The images of cantilever amplitude are also visualized and analysed when the SiOx surface is excited at a fixed frequency. The results show that the acoustic amplitude images can reflect the elastic properties of the sample.
基金supported by the National Basic Research Program of China(2012CB933001)the National Natural Science Foundation of China(21173058,21203038)
文摘We investigated the orientations of interface dipole moments of individual non-planar titanyl phthalocyanine(TiOPc)molecules on Cu(111)and Cu(100)substrates using scanning tunneling microscope(STM)and noncontact atomic force microscope(NC-AFM).The dipole moment orientations corresponding to two different configurations of individual TiOPc molecules were determined unambiguously.The correlation between the actual molecular structures and the corresponding STM topographies is proposed based on the sub-molecular resolution imaging and local contact potential difference(LCPD)measurements.Comparing with the pristine substrate,the LCPD shift due to the adsorption of non-planar molecule is dependent on the permanent molecular dipole,the charge transfer between the surface and the molecule,and the molecular configurations.This work would shed light on tailoring interfacial electronic properties and controlling local physical properties via polar molecule adsorption.
基金This research is financially supported by the National Natural Science Foundation of China(No.51527901).
文摘Dynamic friction occurs not only between two contact objects sliding against each other,but also between two relative sliding surfaces several nanometres apart.Many emerging micro-and nano-mechanical systems that promise new applications in sensors or information technology may suffer or benefit from noncontact friction.Herein we demonstrate the distance-dependent friction energy dissipation between the tip and the heterogeneous polymers by the bimodal atomic force microscopy(AFM)method driving the second order flexural and the first order torsional vibration simultaneously.The pull-in problem caused by the attractive force is avoided,and the friction dissipation can be imaged near the surface.The friction dissipation coefficient concept is proposed and three different contact states are determined from phase and energy dissipation curves.Image contrast is enhanced in the intermediate setpoint region.The work offers an effective method for directly detecting the friction dissipation and high resolution images,which overcomes the disadvantages of existing methods such as contact mode AFM or other contact friction and wear measuring instruments.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11290165,11305252,and U1532260)the Knowledge Innovation Program of the Chinese Academy of Sciences,China(Grant No.KJZD-EW-M03)the Key Research Program of Frontier Sciences,Chinese Academy of Sciences,China(Grant No.QYZDJ-SSW-SLH019)
文摘The properties and stability of the reported surface nanobubbles are related to the substrate used and the generation method. Here, we design a series of experiments to study the influence of the hydrophobicity of the substrate and the produc- tion method on the formation and properties of nanobubbles. We choose three different substrates, dodecyltrichlorosilane （DTS） modified silicon, octadecyltrichlorosilane （OTS） modified silicon, and highly oriented pyrolytic graphite （HOPG） as nanohubble substrates, and two methods of ethanol-water exchange and 4-℃ cold water to produce nanobubbles. It is found that using ethanol-water exchange method could produce more and larger nanobubbles than the 4-℃ cold water method. The contact angle of nanobubbles produced by ethanol-water exchange depends on the hydrophobicity of sub- strates, and decreases with the increase of the hydrophobicity of substrates. More interestingly, nanoscopic contact angle approaches the macroscopic contact angle as the hydrophobicity of substrates increases. It is believed that these results would be very useful to understand the stability of surface nanobubbles.
