Quartz Crystal Microbalance
QCM is a novel Tiny Mass detection instrument dating from the 1960s. Q CM is not a mechanical technique, as the frequency vibrations are measured in thin gold - coated quartz crystals. The QCM mass sensor is one of the most important components of a high-resolution quartz crystal microscopy system. [Sources: 7, 9]
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AT-Cut Quartz for QCM Sensors
A researcher contacted us for AT-Quartz: I work with a research lab and we are trying to buy a range of blank quartz crystals that are AT cut and between 0.1 to 0.5 millimeters in thickness. I don't think the seed is important, we just want blank quartz discs so that we can alter them ourselves for making QCM sensors.
We are very open on the diameter since we intend on cutting them down ourselves. The normal diameters I see being used seem to be in the 4 to 6 inches range so any of those would work. For dimensions, circular wafers are fine. The thickness should be on the order of 0.1, 0.2, 0.3, 0.4, 0.5 millimeters, since this is a parameter we are trying to explore. We would be ordering a number of wafers at each thickness and since the work is experimental in nature we would probably need a lot. My advisor just wanted me to get a quote so maybe you can provide costs for quantities of 25 or 50? The wafers should be double-polished.
Please let me know if you need any other information.
We quoted the wafers to the right.
What Are Quartz Crystal Microbalance (QCM) Sensors?
Quartz Crystal Microbalance (QCM) sensors are highly sensitive devices used to measure extremely small mass changes on a surface by monitoring frequency shifts in oscillating quartz crystals. QCM technology is widely used in thin film deposition, semiconductor processing, biosensing, surface chemistry, vacuum coating systems, and material adsorption studies.
QCM sensors commonly use AT-cut quartz wafers because of their excellent frequency stability, temperature performance, and piezoelectric properties. When material accumulates on the quartz surface, the resonance frequency changes proportionally to the deposited mass.
AT-Cut Quartz Wafers Used for QCM Sensors
Researchers and manufacturers use ultra-flat double-side polished quartz substrates to fabricate high-precision QCM sensors for vacuum deposition monitoring and thin film analysis.
Common AT-cut quartz wafer specifications for QCM applications include:
| Diameter | Orientation | Thickness | Polish | Primary Flat | Grade | Seed | Top Side Ra | Back Side Ra |
|---|---|---|---|---|---|---|---|---|
| 100 ± 0.3 mm | AT-Cut | 0.1 ± 0.03 mm | DSP | 32.5 ± 2.5 mm | SAW | With Seed | <1 nm | <1 nm |
| 100 ± 0.3 mm | AT-Cut | 0.2 ± 0.03 mm | DSP | 32.5 ± 2.5 mm | SAW | With Seed | <1 nm | <1 nm |
| 100 ± 0.3 mm | AT-Cut | 0.3 ± 0.03 mm | DSP | 32.5 ± 2.5 mm | SAW | With Seed | <1 nm | <1 nm |
| 100 ± 0.3 mm | AT-Cut | 0.4 ± 0.03 mm | DSP | 32.5 ± 2.5 mm | SAW | With Seed | <1 nm | <1 nm |
| 100 ± 0.3 mm | AT-Cut | 0.5 ± 0.03 mm | DSP | 32.5 ± 2.5 mm | SAW | With Seed | <1 nm | <1 nm |
| 150 ± 0.3 mm | AT-Cut | 0.2 ± 0.03 mm | DSP | 57.5 ± 2.5 mm | SAW | With Seed | <1 nm | <1 nm |
| 150 ± 0.3 mm | AT-Cut | 0.35 ± 0.03 mm | DSP | 57.5 ± 2.5 mm | SAW | With Seed | <1 nm | <1 nm |
| 150 ± 0.3 mm | AT-Cut | 0.4 ± 0.03 mm | DSP | 57.5 ± 2.5 mm | SAW | With Seed | <1 nm | <1 nm |
| 150 ± 0.3 mm | AT-Cut | 0.5 ± 0.03 mm | DSP | 57.5 ± 2.5 mm | SAW | With Seed | <1 nm | <1 nm |
How Quartz Crystal Microbalance Sensors Work
QCM sensors operate using the piezoelectric properties of quartz crystals. When an alternating voltage is applied across the quartz wafer, the crystal oscillates at a highly stable resonant frequency.
As material accumulates on the sensor surface, the oscillation frequency decreases. This frequency shift allows researchers to calculate mass changes with extremely high sensitivity.
The relationship between deposited mass and frequency shift is commonly described using the Sauerbrey equation, which is widely used in thin film deposition monitoring and surface adsorption measurements.
Applications of QCM Sensors
Quartz Crystal Microbalance technology is used across many scientific and industrial fields requiring precise surface analysis and deposition control.
- Thin film deposition monitoring
- Vacuum coating systems
- Semiconductor process control
- Biosensor development
- Surface adsorption studies
- Nanomaterial characterization
- Chemical sensing
- Plasma deposition systems
- Optical coating analysis
Researchers frequently use QCM sensors alongside thin film deposition systems, CVD processing, and vacuum-compatible semiconductor materials.
Why AT-Cut Quartz is Used for QCM Sensors
AT-cut quartz is commonly selected for QCM applications because it provides excellent frequency stability near room temperature and minimizes temperature-induced frequency drift.
Advantages of AT-cut quartz wafers include:
- High frequency stability
- Excellent piezoelectric performance
- Low temperature sensitivity
- High surface quality
- Low defect density
- Excellent polishing characteristics
Double-side polished quartz wafers with ultra-low surface roughness are especially important for high-precision QCM sensor fabrication and deposition monitoring applications.