共查询到20条相似文献,搜索用时 15 毫秒
1.
The effects of surface functionality and relative humidity (RH) on nanomechanical contact stiffness were investigated using atomic force acoustic microscopy (AFAM), a contact scanned-probe microscopy (SPM) technique. Self-assembled monolayers (SAMs) with controlled surface energy were studied systematically in a controlled-humidity chamber. AFAM amplitude images of a micropatterned, graded-surface-energy SAM sample revealed that image contrast depended on both ambient humidity and surface energy. Quantitative AFAM point measurements indicated that the contact stiffness remained roughly constant for the hydrophobic SAM but increased monotonically for the hydrophilic SAM. To correct for this unphysical behavior, a viscoelastic damping term representing capillary forces between the tip and the SAM was added to the data analysis model. The contact stiffness calculated with this revised model remained constant with RH, while the damping term increased strongly with RH for the hydrophilic SAM. The observed behavior is consistent with previous studies of surface energy and RH behavior using AFM pull-off forces. Our results show that surface and environmental conditions can influence accurate measurements of nanomechanical properties with SPM methods such as AFAM. 相似文献
2.
L. Palacio P. Prádanos A. Hernández M.J. Ariza J. Benavente M. Nyström 《Applied Physics A: Materials Science & Processing》2001,73(5):555-560
The surfaces of three commercial urea formaldehyde polysulfone membranes from Dow DenmarkTM (GR51, GR61 and GR81) are characterised both topographically and chemically. Their topography is studied by scanning force
microscopy to obtain the corresponding pore-size distributions, which are in fair agreement with nominal molecular weight
cut-offs.
The composition of the surfaces of the membranes is analysed by X-ray photoelectron spectroscopy. The resulting percentage
content of nitrogen, which could be attributed probably to an additive used in the manufacturing process, is shown to correlate
with the portion of the total surface with different viscoelastic properties as investigated by using phase-contrast scanning
force microscopy. Both parameters are increasing for membranes with decreasing molecular weight cut-off. Also, the additive
seems to be more sparsely distributed for the membranes with bigger pores, according to fractal analysis. Finally, all the
membranes are very similarly wettable.
Received: 22 May 2001 / Accepted: 30 May 2001 / Published online: 25 July 2001 相似文献
3.
Mariana Köber Enrique Sahagún Martina Fuss Fernando Briones Mónica Luna Juan José Sáenz 《固体物理学:研究快报》2008,2(3):138-140
The effects of adhesion hysteresis in the dynamic‐dissipation curves measured in amplitude‐modulation atomic force microscopy are discussed. Hysteresis in the interaction forces is shown to modify the dynamics of the cantilever leading to different power dissipation curves in the repulsive and attractive regimes. Experimental results together with numerical simulations show that power dissipation, as measured in force microscopy, is not always proportional to the energy dissipated in the tip–sample interaction process. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
4.
Nonlinear optical and electrostatic force microscopy for ferroelectric polarization imaging 总被引:1,自引:0,他引:1
E.D. Mishina N.E. Sherstyuk K.A. Vorotilov A.S. Sigov R. Barberi M.P. Moret F. Manders M.P. De Santo P.K. Larsen T. Rasing 《Applied physics. B, Lasers and optics》2002,74(7-8):783-788
Second-harmonic generation (SHG)-based nonlinear optical microscopy is used for spatially resolved imaging of the polarization
switching in lead zirconium titanate ferroelectric thin films. The local SHG hysteresis loops reveal a strong dependence on
film composition and structure. The SHG microscopy results are in good agreement with the efficiency of electrostatic force
microscopy writing and allow us to predict the microscopic dielectric memory efficiency, both in contact and contact-less
ways.
Received: 15 January 2001 / Revised version: 27 March 2002 / Published online: 6 June 2002 相似文献
5.
S. Myhra 《Applied Physics A: Materials Science & Processing》2003,76(1):63-69
Three mechanisms for spatially resolved growth and removal of oxide on silicon substrates have been investigated. Thermally
grown oxide layers with thicknesses in the range 2–6 nm were the distinctive feature of the system. The layers were characterized
and manipulated by methodologies based on atomic force microscopy (AFM) with conducting probes in a vacuum environment of
10-2–10-3 Pa. The probe is then effectively a travelling electrode that generates an electrostatic field between the tip and the substrate.
Oxide growth was induced for a positive sample bias greater than 5 V, but below the level corresponding to dielectric breakdown.
Application of a short pulse of amplitude marginally above that corresponding to dielectric breakdown, on the other hand,
had the effect of producing pits of inner diameter of about 10 nm in the pre-existing oxide layer at the point of tip-to-oxide
contact. Application of a low positive sample bias (less than that required for measurable oxide growth) in combination with
high linear scan speed had the effect of removing a pre-existing oxide layer from the scanned field of view. The most plausible
mechanisms are based on transverse ionic diffusion (for oxide growth), controlled dielectric breakdown (for formation of pits)
and lateral transport of silicaceous species (for oxide removal).
Received: 24 October 2001 / Accepted: 6 January 2002 / Published online: 3 June 2002
RID="*"
ID="*"Corresponding author. Fax: +617-3875-7656, E-mail: s.myhra@sct.gu.edu.au 相似文献
6.
X.N. Jiang D. Xu D.R. Yuan D.L. Sun M.K. Lu M.H. Jiang 《Applied Physics A: Materials Science & Processing》2002,75(5):617-620
Atomic force microscopy (AFM) has been used to investigate the phase transitions and surface morphology transformation of
cadmium mercury thiocyanate (CMTC) crystals, which are highly efficient nonlinear optical (NLO) materials for generating blue-violet
light by laser frequency doubling. Amorphous aggregates at the crystalline steps become greatly contracted and much more crystalloid
after the crystal was kept for one day. Elimination of dangling bonds, which lower the surface free energy at the crystal
surface, and structural adjustment inside the crystal are assumed to cause this phase transition. Surface morphology transformations
were also observed in CMTC crystals during and after multiple scanning by AFM tips. We have visualized the continuous translation
process from two-dimensional nuclei to trigonal microcrystals with almost equal sizes during multiple scanning. In other cases,
however, the surface morphology did not change at all during scanning, but became greatly altered hours after scanning. These
experimental results suggest that reconstruction is a characteristic growth phenomenon on CMTC crystal surfaces. Reconstruction
probably results from the formation of intervening metastable phases that have the potential to arrive at more stable stages;
however, multiple scanning of AFM tips greatly affects this translation process.
Received: 28 August 2001 / Accepted: 7 November 2001 / Published online: 29 May 2002 相似文献
7.
J.H. Müller U.D. Schwarz R. Wepf R. Wiesendanger 《Applied Physics A: Materials Science & Processing》2003,76(6):893-898
We present the design of a new scanning force microscope specially suited for the investigation of soft matter, particularly
biological, in an ultrahigh vacuum. The key point is that the samples are immobilized by shock freezing in order to maintain
their native structure before they are introduced into the vacuum system. The vacuum system itself consists of a transfer
chamber, which allows an exchange of the cold sample with cryo-electron microscopes, a preparation chamber including a stage
for in-situ freeze drying, freeze etching, or freeze fracturing, and the analysis chamber with the microscope. Sample cooling
is maintained in all chambers. The microscope is mounted on a commercially available vibration isolation system; a flow cryostat
cools the sample to the temperature of liquid nitrogen, while the tip is scanned. Besides measurements on test samples, which
demonstrate the imaging capabilities of the instrument, first results on T4-bacteriophages (viruses) are shown.
Received: 2 September 2002 / Accepted: 2 September 2002 / Published online: 5 March 2003
RID="*"
ID="*"Corresponding author. Fax: +49-40/42838-6188, E-mail: wiesendanger@physnet.uni-hamburg.de 相似文献
8.
Sheng-Rui Jian 《Applied Surface Science》2008,254(21):6749-6753
Presented in this study are the Berkovich nanoindentation-induced mechanical deformation mechanisms of metal-organic chemical-vapor deposition (MOCVD) derived GaN thin films, investigated by using the cathodoluminescence (CL) and the cross-sectional transmission electron microscopy (XTEM) techniques. The multiple “pop-in” events were observed in the load-displacement (P-h) curves and appeared to occur randomly with increasing the indentation load. These instabilities are attributed to the dislocation nucleation and propagation. CL images of nanoindentation show a very well-defined rosette structures with the hexagonal system, and clearly display the distribution of deformation-induced extended defects/dislocations which affect CL emission. By using focused ion beam (FIB) milling to accurately position the cross-section of an indented area, XTEM results demonstrate that the major plastic deformation is taking place through the propagation of dislocations. The present observations are in support to the massive dislocations activities occurring underneath the indenter during the loading cycle. No evidence of either phase transformation or formation of micro-cracking was observed by using XTEM observations. We also discuss how these features correlate with Berkovich nanoindentation-induced defects/dislocations microstructures. Finally, this study has significant implications for the extent of contact-induced damage during fabrication of GaN-based optoelectronic devices. 相似文献
9.
T.I. Kamins K. Nauka R.S. Williams 《Applied Physics A: Materials Science & Processing》2001,73(1):1-9
Incorporating self-assembled Ge islands on Si surfaces into electronic devices has been suggested as a means of forming small
features without fine-scale litho-
graphy. For use in electronic devices, the electrical properties of the deposited Ge and their relation to the underlying
Si substrate must be known. This report presents the results of a surface photovoltage investigation of the surface energy
barrier as increasing amounts of Ge are added to a Si surface by chemical vapor deposition. The results are interpreted in
terms of band discontinuities and surface states. The surface barrier increases as a wetting layer is deposited and continues
to increase as defect-free islands form. It saturates as the islands grow. As the amount of Ge continues increasing, defects
form, and the surface barrier decreases because of the resulting allowed states at the Ge/Si interface. Qualitatively similar
behavior is found for Si(001) and Si(111). Covering the Ge with Si reduces the surface-state density and possibly modifies
the wetting layer, decreasing the barrier to one more characteristic of Si. Initial hydrogen termination of the surface decreases
the active surface-state density. As the H desorbs, the surface barrier increases until it stabilizes as the surface oxidizes.
The behavior is briefly correlated with scanning-tunneling spectroscopy data.
Received: 13 November 2000 / Accepted: 14 November 2000 / Published online: 23 May 2001 相似文献
10.
Application of scanning force microscopy in nanotube science 总被引:2,自引:0,他引:2
J. Muster G.S. Duesberg S. Roth M. Burghard 《Applied Physics A: Materials Science & Processing》1999,69(3):261-267
Recent developments in the application of scanning force microscopy in nanotube science are reviewed. The non-destructive
character of this technique allows the structural characterisation of (chemically modified) single- and multi-wall nanotubes
deposited on substrates for further investigations such as electrical transport measurements. Furthermore, SFM is now an established
tool for manipulation of nanotubes, which allows position control and determination of elastic constants such as the Young’s
modulus. Finally it is shown that very sharp and stable probes for scanning force microscopy can be made from nanotubes due
to their excellent stability and aspect ratio.
Received: 17 May 1999 / Accepted: 18 May 1999 / Published online: 29 July 1999 相似文献
11.
M. Andersson A. Iline F. Stietz F. Träger 《Applied Physics A: Materials Science & Processing》1999,68(5):609-614
Gold films with a nominal thickness of 5–40 monolayers were grown on dielectric substrates and imaged by scanning force microscopy
(SFM). The films originally consisted of well-separated or densely packed clusters. During imaging in contact mode, the morphology
of the films changed drastically. At low coverage, i.e. Θ<10 monolayers, the well-known stripes originating from mobile clusters,
eventually accumulated into larger aggregates, were observed. In contrast, at larger coverage, highly ordered structures consisting
of one-dimensional wires evolved during scanning. They often were parallel with equal separation, i.e. well-defined periodicity,
over distances of several μm. Typically, the wires were 5–10 nm high and 50–100 nm wide. Investigations of Au films prepared
at varying temperature on different dielectric substrates allow us to suggest a self-assembling mechanism for wire formation
in which gold is periodically collected by the SFM tip and redeposited as soon as a critical amount is reached.
Received: 22 February 1999 / Accepted: 2 March 1999 / Published online: 7 April 1999 相似文献
12.
In this paper, we describe a statistical method of quantification of the number of functional groups at the contact area of a probe tip for atomic force microscopy from the result of repetitive pull-off force measurements. We have investigated laboratory-made carbon nanotube (CNT) probe tips to apply them for chemical force microscopy because limited number of functional groups at the tip-end is expected. Using a CNT tip, we conducted repetitive pull-off force measurements against a self-assembled monolayer terminated with carboxyl group and analyzed them in terms of the number of hydrogen bond groups at the CNT tip. The elementary hydrogen bond rupture force quantum in n-decane medium was estimated to be 84.2 ± 0.5 pN in the present system. Thus it was revealed that only a couple of hydrogen bond groups of the CNT tip were participating in hydrogen bonding with the sample on an average in this experimental system. 相似文献
13.
J. Hone M.C. Llaguno M.J. Biercuk A.T. Johnson B. Batlogg Z. Benes J.E. Fischer 《Applied Physics A: Materials Science & Processing》2002,74(3):339-343
The thermal properties of carbon nanotubes are directly related to their unique structure and small size. Because of these
properties, nanotubes may prove to be an ideal material for the study of low-dimensional phonon physics, and for thermal management,
both on the macro- and the micro-scale. We have begun to explore the thermal properties of nanotubes by measuring the specific
heat and thermal conductivity of bulk SWNT samples. In addition, we have synthesized nanotube-based composite materials and
measured their thermal conductivity.
The measured specific heat of single-walled nanotubes differs from that of both 2D graphene and 3D graphite, especially at
low temperatures, where 1D quantization of the phonon bandstructure is observed. The measured specific heat shows only weak
effects of intertube coupling in nanotube bundling, suggesting that this coupling is weaker than expected. The thermal conductivity
of nanotubes is large, even in bulk samples: aligned bundles of SWNTs show a thermal conductivity of >200 W/m K at room temperature.
A linear K(T) up to approximately 40 K may be due to 1D quantization; measurement of K(T) of samples with different average
nanotube diameters supports this interpretation.
Nanotube–epoxy blends show significantly enhanced thermal conductivity, showing that nanotube-based composites may be useful
not only for their potentially high strength, but also for their potentially high thermal conductivity.
Received: 17 October 2001 / Accepted: 3 December 2001 / Published online: 4 March 2002 相似文献
14.
Asymmetric PS-b-PEO block copolymer exhibits well-ordered cylindrical morphology with nanoscale domain sizes due to microphase separation. Since the PS and PEO blocks have large stiffness difference, this polymer system represents an ideal candidate for studies of the phase contrast behavior in atomic force microscopy (AFM). In this paper, PS-b-PEO films are investigated under different scanning conditions using two different atomic force microscopes. It is found that the phase contrast of the film can be well described in terms of energy dissipation, though the exact phase image may also depend on the scanning parameters (e.g., the repulsive versus attractive regimes) as well as the settings of the microscope. Height variation on sample surface does not have significant effect on phase contrast. However, in order to obtain true topography of the polymer film, care has to be taken to avoid damage to the sample by AFM. Under certain conditions, true topography can be obtained during the first scan in spite of the surface-damaging forces are used. 相似文献
15.
The effect of the surface characteristics of Ni catalyst films on the growth behavior of multi-walled carbon nanotubes (MWCNTs) were investigated using Ni catalyst films prepared by different physical vapor deposition methods, electron-beam evaporation and sputtering. The growth behavior of MWCNTs was dependent upon the surface roughness of the Ni films. After a pretreatment process with NH3, the root mean squares of surface roughness of e-beam evaporated and sputtered Ni catalyst films increased to 16.6 and 3.2 nm, respectively. Curled-MWCNTs and carbon-encapsulated Ni nanoparticles were formed on the Ni film deposited by e-beam evaporation while vertically aligned-MWCNTs were grown on the sputter-deposited film. In addition, the surface roughness of the Ni films affected the field emission properties of the MWCNTs. This was considered to originate from the specific growth behavior of the MWCNTs which was primarily caused by the initial surface roughness of the Ni films. 相似文献
16.
J.J. Kolodziej B. Such M. Goryl F. Krok P. Piatkowski M. Szymonski 《Applied Surface Science》2006,252(21):7614-7623
Surfaces of several AIIIBV compound semiconductors (InSb, GaAs, InP, InAs) of the (0 0 1) orientation have been studied with noncontact atomic force microscopy (NC-AFM). Obtained atomically resolved patterns have been compared with structural models available in the literature. It is shown that NC-AFM is an efficient tool for imaging complex surface structures in real space. It is also demonstrated that the recent structural models of III-V compound surfaces provide a sound base for interpretation of majority of features present in recorded patterns. However, there are also many new findings revealed by the NC-AFM method that is still new experimental technique in the context of surface structure determination. 相似文献
17.
Silver selenide thin films were grown on silicon substrates by the solid-state reaction of sequentially deposited Se and Ag films of suitable thickness. Transmission electron microscopy and particle-induced X-ray emission studies of the as-deposited films showed the formation of single phase polycrystalline silver selenide from the reaction of Ag and Se films. Atomic force microscopy images of the as-deposited and films annealed at different temperatures in argon showed the film morphology to evolve into an agglomerated state with annealing temperature. The results indicate that when annealed above 473 K, silver selenide films on silicon become unstable and agglomerate through holes generated at grain boundaries. 相似文献
18.
G. Appel H. Ade A.G. Guerek S. Stadler R.P. Mikalo D. Schmeisser 《Applied Physics A: Materials Science & Processing》2003,76(2):177-182
Layers of dihydroxy silicon phthalocyanine tetrasulfonic acid and oligo-μ-oxo silicon phthalocyanine tetrasulfonic acid were
prepared by solution-casting methods. The purity of the material was checked by X-ray photoemission spectroscopy. The orientation
of the molecules in respect to the substrate plane was investigated by angle-dependent near-edge X-ray absorption fine-structure
spectroscopy. The morphology was characterized by atomic force microscopy. Most samples exhibited a significant orientation
that was accompanied by crystalline structures; others had no orientation at all with a dominant amorphous morphology. This
behavior indicates that several preparation parameters affect the crystallinity and the orientation of the phthalocyanines.
Received: 16 January 2002 / Accepted: 11 February 2002 / Published online: 3 May 2002
RID="*"
ID="*"Corresponding author. Fax: +1-919/515-7331, E-mail: harald_ade@ncsu.edu
RID="**"
ID="**"Present address: Southern Illinois University, Physics, Mailcode 4401, Carbondale, IL 62901, USA 相似文献
19.
K.H. Heinig T. Müller B. Schmidt M. Strobel W. Möller 《Applied Physics A: Materials Science & Processing》2003,77(1):17-25
We have investigated the synthesis of nanostructures, as well as the control of their size and location by means of ion beams.
The phase separation and interface kinetics under ion irradiation give new possibilities for controlling the growth of nanostructures.
Additionally, the chemical decomposition of the host matrix by collisional mixing can contribute to the self-organization
of nanostructures, especially at interfaces. It is shown how collisional mixing during ion implantation affects nanocrystal
(NC) synthesis and how ion irradiation through NCs modifies their size and size distribution. An analytical expression for
solute concentration around an ion-irradiated NC was found, which may be written like the well-known Gibbs–Thomson relation.
However, parameters have modified meanings, which has a significant impact on the evolution of NC ensembles. “Inverse Ostwald
ripening” of NCs, resulting in an unimodal NC size distribution, is predicted, which has been confirmed experimentally for
Au NCs in SiO2 and by kinetic lattice Monte Carlo simulations. At interfaces, the same ion-irradiation-induced mechanism may result in self-organization
of NCs into a thin δ-layer. Collisional decomposition of SiO2 may enhance the NC δ-layer formation in SiO2 at the Si/SiO2 interface. The distance of the self-organized NC δ-layer from the SiO2/Si interface renders the structure interesting for non-volatile memory applications.
Received: 11 November 2002 / Accepted: 12 November 2002 / Published online: 4 April 2003
RID="*"
ID="*"Corresponding author. Fax: +49-351-260-3285, E-mail: K.-H.Heinig@fz-rossendorf.de 相似文献
20.
C. Teichert J.C. Bean M.G. Lagally 《Applied Physics A: Materials Science & Processing》1998,67(6):675-685
Received: 30 July 1998/Accepted: 23 October 1998 相似文献