The Stanford Research Systems QCM100 is a quartz crystal microbalance (QCM) instrument that measures mass and viscosity changes at surfaces and within thin films in real time. Operating at 5 MHz with an AT-cut quartz resonator, it detects mass variations from fractions of a nanogram to micrograms, with sensitivity extending to sub-monolayers of atoms. The system quantifies both frequency shifts—proportional to deposited mass—and changes in series resonance resistance, which correlate directly to material viscosity and elasticity. A Q-factor exceeding 60,000 in liquid environments ensures measurement stability even in demanding chemical and biological applications.
Technical Specifications
• Resonator Frequency: 5 MHz nominal, AT-cut plano-plano geometry
• Crystal Diameter: 1 inch
• Mass Detection Range: Fractions of a nanogram to micrograms
• Detection Limit: Sub-monolayers of atoms
• Heavy Load Capability: Maintains oscillation up to 5 kΩ resistance
• Aqueous Stability: Sustained operation in solutions exceeding 88% glycerol (w/w)
• Q-Factor: >60,000 typical in liquid environments
• Crystal Surface Finish: Optical polish (<10 Å RMS)
• Electrode Materials: Cr/Au standard; Ti/Au, Ti/Pt, and ITO optional
• Frequency Output: 2.4 Vpp square wave, 50 Ω, TTL levels
• Conductance Output (Vc): 0 to 10.625 VDC, 1 kΩ source impedance
– Key Features
• Measures resonant frequency shifts linearly proportional to surface mass deposition
• Converts resistance changes to viscosity and elasticity data via: R = 10,000 × (10 – Vc/5) – 75 Ω
• Flat (non-planoconvex) crystal geometry for uniform measurement fields
• Compatible with liquid and gas environments through compact crystal holder
• Supports alternative frequencies (6 MHz, 9 MHz) and specialized electrode coatings
– Typical Applications
• Thin-film deposition monitoring
• Corrosion studies
• Biosensing and biofilm characterization
• Chemical sensing and detection
– Compatibility & Integration
The complete system comprises the QCM100 analog controller, QCM25 crystal oscillator, crystal holder, and three 5 MHz quartz crystals. External instrumentation required: precision frequency counter for frequency measurement and high-resolution digital voltmeter (minimum 6-digit resolution with computer interface) for conductance measurement.
