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X-ray Reflectivity
Types of Techniques
- Inductively coupled plasma-optical emission spectrometry (ICP-OES)
- UV-Vis spectroscopy
- X-Ray fluorescence (XRF)
- Atomic absorption spectroscopy (AAS)
- Time-Resolved Photoluminescence Spectroscopy (TRPL)
- X-Ray Photoelectron Spectroscopy (XPS)
- Auger Electron Spectroscopy (AES)
- Fourier Transform Infrared Spectroscopy (FTIR)
- Atomic Fluorescence Spectroscopy (AFS)
- Infrared (IR) spectroscopy
- Nuclear Magnetic Resonance Spectroscopy
- Time of Flight Secondary Ion Mass Spectrometry (Tof-SIMS)
- Spectrophotometer
- Mössbauer Spectroscopy
- ultra violet photoelectron spectroscopy
- Electron Paramagnetic Resonance (EPR)
- Glow Discharge Optical Emission Spectrometry
- X-ray Reflectivity (XRR)
- Total Reflection-TXRF
- Ion scattering spectroscopy (ISS)
- Rutherford Backscattering Spectrometry (RBS)
- ToF Elestic Recoil Detection
- Spectroscopic Ellipsometry
X-ray Reflectivity (XRR)
X-ray Reflectivity (XRR), an analytical technique akin to X-ray Diffraction (XRD), is increasingly recognized for its efficacy in evaluating thin-film and multilayer structures. By examining X-ray scattering at extremely small diffraction angles, it enables the detailed characterization of electron density profiles within thin films, even those as thin as a few tens of angstroms. Through simulating the reflectivity pattern, XRR offers precise measurements of thickness, interface roughness, and layer density, applicable to both crystalline and amorphous thin films and multilayers. Notably, XRR eliminates the need for prior assumptions about the optical properties of the films, distinguishing it from techniques like optical ellipsometry.
Three primary types of information that can be derived from XRR curves:- Density: Determined by the critical angle associated with total reflection, which varies based on the surface material’s density.
- Surface layer thickness: Evidenced by oscillations in the data, reflective of deposited film frequency. Thicker films result in shorter oscillation periods.
- Surface roughness: Linked to the decline in XRR signal; higher roughness correlates with faster decay in reflected X-rays. In essence, increased film roughness accelerates the rate of X-ray reflectivity decay.
The basic principle of X-ray Reflectivity (XRR) involves directing a beam of X-rays onto a flat surface and measuring the intensity of X-rays reflected at the same angle as the incident beam. Any deviation from the expected intensity, as predicted by the Fresnel reflectivity law, indicates surface imperfections or irregularities. Analyzing these deviations, typically caused by surface roughness and interfacial inconsistencies, allows for the determination of the density profile perpendicular to the surface. Consequently, this technique yields comprehensive insights into film thickness, density, and roughness, proving indispensable for the characterization of thin films and multilayers.
- Sensor Development: Development and characterization of thin film sensors used in precision agriculture.
- Packaging Materials: Analysis of thin film materials used in agricultural packaging to enhance durability and protection.
- Biocompatible Coatings: Evaluation of coatings on medical implants to ensure they meet required standards for thickness and surface properties.
- Membrane Studies: Analysis of biological membranes and other thin film structures used in medical applications.
- Thin Film Polymers: Determining the thickness and uniformity of polymer films used in various applications.
- Surface Treatments: Assessing the effectiveness of surface treatments and coatings on polymer materials.
- Photovoltaic Cells: Characterization of thin film layers in solar cells to optimize performance.
- Battery Materials: Analysis of thin films used in battery electrodes to improve energy storage capacity and efficiency.
- Nanostructure Analysis: Characterization of nanometre-scale thin films and multilayers, crucial for nanodevice fabrication.
- Interface Studies: Understanding the interfaces in nanocomposite materials and their impact on material properties.
- Surface Characterization: Analysis of surface and interface roughness, essential for developing new materials.
- Layered Structures: Investigation of multilayer coatings, including their thickness, density, and interfacial properties.
- Thin Film Analysis: Measurement of film thickness, density, and roughness in semiconductor layers.
- Quality Control: Monitoring the uniformity and quality of deposition processes for microelectronics fabrication.
- Evaluating Tablet Wettability for disintegration testing.
- Measuring Surface Tension of drug delivery vehicles.
- Analysing Dissolution Properties of pharmaceutical ingredients.
- Protective Coatings: Evaluation of thickness and uniformity of protective coatings used in various industries.
- Optical Coatings: Analysis of coatings used in optical devices to ensure desired optical properties are achieved.
- Enables analysis of entire wafers, including those up to 300 mm in diameter, as well as irregular and large samples.
- Facilitates mapping of complete wafers.
- Capable of analyzing both conductive and insulating materials.
- Accuracy in determining film thickness is independent of prior knowledge of the film’s optical properties.
- Requires minimal or no sample preparation.
- Analysis can be conducted under ambient conditions.
Samples must exhibit high smoothness and flatness, with surface roughness typically below a few hundred nanometers. Consequently, this method primarily finds utility in characterizing thin films and coatings on exceptionally flat substrates such as silicon chips and semiconductor materials.