INTRODUCTION
History of Scanning Probe Microscopy
Scanning probe microscopy (SPM) began with the invention of the scanning tunneling microscope (STM) in 1982 by Binning and Rohrer of IBM, Zurich.1 The impact that the invention of SPM would have on characterization at the nanoscale was clear and led to the award of the Nobel Prize in Physics to Binning and Rohrer in 1986. The first commercial AFM was not available until the late 1980s, making SPM a relatively new analytical technique.
Advantages of AFM
The development of SPM has enabled scientists and engineers to see structure and detail with unparalleled resolution in three dimensions without the need for rigorous sample preparation. For a complete description of the different AFM modes and the many applications of AFM, see the recent article by Jandt.3.
Limitations of AFM
Isolation becomes more critical the higher the resolution required and the smoother the surface being evaluated. Charging glass surfaces can cause problems with sufficient contact between the tip and the sample and lead to poor results.
Use of AFM in the Study of Glasses
- Examples of General AFM Studies of Glasses
- Study of Optical Fibers
- High Resolution Study of Glass Surfaces
- Chemical Force Microscopy and Glasses
The surface topography of cleaved and etched optical fibers is related to the chemical composition profile and thus to the refractive index of the fiber. Core, cladding and interface structures can be studied with unsurpassed spatial resolution.
The evolution of the point height is the only consequence of the difference in the etching rate of the core (dco) and the cladding (dcl). Very small increases in the size of the inhomogeneities resulted in the shorter heat treatment times at 650°C. AFM was used to assess the surface area of the copper oxide thin film formed on the Glass Lab sample.
The effect of the level of copper oxide in the glass on the glass transition temperature is shown in Figure 5.15. Analysis of the 530°C heat treatment was not complete due to the observation of bulk crystallization. The vacuum in the sample tube was better than 10 millitorr for the duration of the heat treatment.
An analysis of the depth profile in Fig. 5.38 and the fact that the spreading rate was.
EXPERIMENTAL PROCEDURE
Atomic Force Microscopy
The forces between the tip and the sample surface change the motion of the cantilever, causing it to bend or change the amplitude of the oscillation. In contact mode imaging, the cantilever is maintained in the van der Waals repulsive region and induces the highest interactive forces between the tip and the sample.
Plot of radial core etch rate and differential etch rate as a function of the value of X in the etch solution. Graph of the relationship between core etch rate and differential etch rate for SMF28 fiber. The composition of solid glass was quantitatively determined using X-ray fluorescence (XRF).
Topography (top) and EFM (bottom) results of the film surface of glass composition CU102903 after heat treatment at 500°C/24 h. The morphology shown in Figure 5.36 is very different from the morphology of the copper oxide surfaces.
UNDERSTANDING THE NEAR-FIELD SCANNING OPTICAL
Abstract
The cone angle was dependent on the concentration of GeO2 in the fiber core as well as the concentration of the etching solution. The final cone angle can be predicted from the differential etch rate between the core and cladding, as well as measuring the angle directly using AFM.
Introduction
- Near-Field Scanning Optical Microscopy Overview
- Modes of NSOM Operation
- Applications of NSOM
- Methods for Producing NSOM Tips
- Fiber Pulling
- Fiber Etching
- Micro-Machined NSOM Tips
- Apertureless NSOM Tips
Laser light coupled to a single-mode optical fiber passes through a sub-wavelength aperture at the end of the fiber. Laser light is coupled into a sub-wavelength aperture, illuminating a sample placed in the near field of the tip.
Experimental Procedures
- Safety Precautions
- Preparation of Etch Solutions
- Fiber Etching Procedures
- Characterization of Etched Fiber End Faces
- Optical Microscopy/Scanning Electron Microscopy
- Atomic Force Microscopy
The majority of the initially etched fiber samples were difficult to characterize due to deposits that formed on the end faces of the fibers during the etching process. Scanning electron microscopy (SEM) images were collected on an Amray 1845FE field emission instrument, using the secondary detector.
Results and Discussion
Initial Study of SMF28 and HI Optical Fibers
They showed that the important physical parameters of the fiber were the core diameter and the differential etch rate between the core and cladding. The faster the cladding is eroded away from the core and the lower the solubility of the core, the sharper the resulting cone angle. From Equation 7, the slope of the lines in Figure 3.10 (Htip/t), is the differential etch rate between the core and cladding, (dcl - dco.
More Detailed Evaluation of the SMF28 Fiber Etching Process
Plot of core height as a function of X value in the etching solution for an etching time of 10 minutes. This chemical variation and its effect on the radial core etch rate was discussed in the introductory section above. Plot of the relationship between radial core etch rate, differential etch rate and taper angle for SMF28 fiber etched in HF buffer solutions.
Conclusions
A very light etch is all that is required due to the exceptional z-resolution of the AFM. Copper oxide has two main forms, depending on the oxidation state of the copper ions. AFM was also used to perform electric force microscopy (EFM) measurements of copper oxide films.
With the spectral reflectance phase used, the percentage transmission is related to the reflectivity of the surface. SEM and AFM analysis were completed on the CU090403 glass to further evaluate the glass surface before and after heat treatment. The high-resolution phase image in Figure 5.23 shows a fairly random orientation of the CuO crystals.
The surface roughness and thickness of the resulting films were evaluated using AFM.
EVALUATION OF PHASE SEPARATION IN GLASSES
Abstract
The presence of phase separation in glasses and the ability to design the shape and scale of the glass microstructure allow the potential to tailor properties of glasses for specific applications. AFM provides rapid and accurate evaluation of the type, degree and scale of phase separation in glasses down to the nanometer level. This paper will present sample preparation techniques and results for evaluating phase separation in alkali borosilicate and sodium silicate glass systems.
Introduction
Phase Separation in Glasses
700°C is in the metastable region of the immiscible dome, resulting in phase separation through the nucleation and growth process. AFM top view, 3D view, and cross-sectional analysis of the CU102903 glass composite film surface heat treated at 500°C/2 h.
Characterization of Phase Separated Glasses
Experimental Procedures
Glass Melting and Sample Preparation
Prior to AFM analysis, the heat-treated cane samples were sectioned and etched to develop surface morphology based on the differential etching properties of the silica phase versus the sodium-rich phase. Light etching, after grinding and polishing, can also be used to create surface topography resulting from the change in chemical stability of the glass phases. Once fractured, a light etch in the appropriate solution will provide the surface topography based on the differential etching properties of the glass phases involved.
Atomic Force Microscopy
The three-dimensional digital image is produced by mapping the motion of the z-piezo required to maintain a constant oscillation amplitude at each lateral data point.
Results and Discussion
Alkali Borosilicate Results
Sodium Silicate Results
To estimate the spatial growth of phases during spinodal decomposition, the Grain Size command from the Nanoscope® software was used. A consistent increase in the area of the high silica phase is shown for heat treatments between 160 min and the longest heat treatment time of 1540 min. Zarzycki and Naudin11 used SAXS to demonstrate that the roughening of the spinodal microstructure increases in proportion to the cube root of the heat treatment time.
Conclusions
XRD did not detect any significant film formation for the as-fused glass, but copper oxide (CuO) was identified on the surface of the heat-treated glass surface. A much less complicated alkali borosilicate glass was used to carry out further research on the copper oxide film formation. AFM top view, 3D view and section analysis of the as-melted surface of glass assembly CU102903.
AFM top view, 3D view and cross-sectional analysis of the film surface of the glass composition CU102903 after heat treatment at 400 °C/24 h. AFM top view, 3D view and cross-sectional analysis of the film surface of glass composition CU102903 after heat treatment at 500 °C/24 h.
THIN FILM COPPER OXIDE LAYERS GROWN IN-SITU ON
Abstract
AFM was used to show that the thickness and uniformity of the copper oxide film increased with time and temperature, but an upper time limit was reached at which there was no further increase in thickness. XPS was used to confirm the formation of a copper oxide film during heat treatment of glasses near Tg, which results from the oxidation of copper ions in the glass from the 1+ state to the 2+ state. Copper ions migrate to the surface from inside the glass to balance the excess positive charge resulting from the oxidation of Cu+ to Cu2+ in the glass.
Introduction
Structure of Alkali Borosilicate Glasses
The formation of copper oxide films grown in-situ on the surface of copper-containing alkali borosilicate glasses was investigated. The effect of alkali substitution was also investigated, and the more acidic glass batches resulted in better film formation, as a result of the majority of the copper ions staying in the +1 state in the more acidic glass melts.
Copper in Glasses
Copper Oxide Films on Glasses
Traditionally, the deposition of copper oxide films on glass has been accomplished by reactive sputtering and vacuum evaporation techniques.12,13 Additional methods that have been reported to produce copper oxide films on glass surfaces include thermal and chemical oxidation of the metal. of copper13-15, sol- gel chemistry,16-19 chemical deposition17,19 and plasma evaporation20. In-situ production of copper oxide films on the surface of copper-containing glasses has been reported for several glass systems, including aluminosilicates,21 lead aluminoborates,22 sodium silicates23 and patent-granted calcium aluminoborosilicates. in 1989.24.
Experimental Procedures
- Sample Preparation
- UV-Vis Spectroscopy
- Scanning Electron Microscopy
- Differential Scanning Calorimetry
- Thermo-gravimetric Analysis
- X-ray Diffraction
- Atomic Force Microscopy
- XPS
At the end of the heat treatment time, the tube was evacuated and then vented back to ambient. The interaction of the beam with the sample generates a series of signals, where the most used are secondary and. An AFM conductive tip interacts with the sample through long-range Coulomb forces, which affect the oscillation amplitude and phase of the AFM cantilever.
Results and Discussion
Initial Characterization of Glass Lab Sample
Even at the lowest acceleration potential, a significant amount of secondary electrons will be generated from the glass beneath the film, resulting in the bulk glass composition that appears in the EDX analysis of the film surface. A bulk sample was sampled and mounted on a bulk sample holder, with the surface of the sample film in the sample plane of the goniometer circle. Although the intensity of the crystalline peaks was still low, XRD analysis determined that the film was copper oxide, CuO also known as the mineral Tenorite.
Characterization of Glass Batch CU090403
For a visual comparison of the surface roughness and uniformity, Figure 5.28 displays the section lines for the longest heat treatments for each temperature. The copper concentration in the heat-treated sample under the CuO layer is twice that of the as-polished glass while the sodium concentration is lower. High resolution XPS Cu 2p spectra of the as-polished sample, comparing chemical state at the surface with that of the bulk.
Characterization of Sodium Borosilicate Glasses
- Effect of Copper Level on Copper Oxide Film Formation
- Heat Treatment Studies of Composition CU102903
- Effect of Heat Treatment Atmosphere on Film Formation
- Mechanism for Copper Oxide Film Formation
- Effect of Alkali on Copper Oxide Film Formation
