Atomic force microscopy (AFM) is a powerful tool for nanoscale surface characterization, capable of operating under various environmental conditions to study material behavior. Two specialized configurations extend its capabilities: humidity/temperature-controlled AFM and vacuum AFM systems. These systems integrate precise environmental control with high-resolution scanning to investigate surface properties under controlled or extreme conditions.

**Humidity/Temperature-Controlled AFM Systems**
Environmental control in AFM is critical for studying materials under conditions mimicking real-world applications or specific thermodynamic states. Humidity/temperature chambers are add-on modules or integrated systems that enclose the AFM probe and sample in a regulated atmosphere.

The instrumentation consists of several key components. A sealed chamber encloses the sample and cantilever, constructed from materials resistant to thermal expansion and corrosion, such as stainless steel or anodized aluminum. Temperature control is achieved using Peltier elements, resistive heaters, or liquid nitrogen cooling, with thermocouples or platinum resistance thermometers providing feedback for stability within ±0.1°C. Humidity is regulated by mixing dry and water-saturated gas streams, typically using mass flow controllers, with capacitive or chilled-mirror hygrometers ensuring precision (±1% RH).

Active vibration isolation and acoustic damping are essential, as environmental chambers can introduce mechanical noise. Anti-vibration tables and passive damping materials minimize external disturbances. The AFM scanner must compensate for thermal drift, often through closed-loop positioning systems with capacitive sensors maintaining nanometer-scale accuracy.

Operational modes include contact, tapping, and peak force tapping, adapted to avoid artifacts from condensation or surface tension effects. Specialized probes with conductive coatings or hydrophobic treatments may be used to reduce meniscus forces in humid environments. Data correlation tools synchronize topographical data with temperature/humidity logs, enabling analysis of dynamic processes like adsorption, swelling, or phase transitions.

**Vacuum AFM Systems**
Vacuum AFM eliminates atmospheric interference, enabling atomic-resolution imaging and measurements of intrinsic material properties without surface contamination. These systems integrate ultrahigh vacuum (UHV) technology with AFM instrumentation.

The vacuum chamber is typically a stainless steel vessel with conflat flanges, achieving base pressures below 1×10⁻⁹ mbar via turbomolecular or ion pumps. Samples and probes are introduced through load-lock systems to maintain vacuum integrity. In-situ cleaning methods, such as argon sputtering or thermal annealing, prepare surfaces before analysis.

The scanner design differs from ambient AFM. Piezoelectric tubes or flexure stages operate in vacuum, where lack of air damping necessitates lower scan speeds to avoid oscillations. Frequency modulation (FM-AFM) or non-contact modes are preferred, using stiff cantilevers (spring constants > 40 N/m) to mitigate van der Waals adhesion. Optical lever detection remains standard, though fiber interferometry is sometimes employed for compactness.

Temperature control in vacuum AFM ranges from cryogenic (4 K) to high temperature (1000°C), using liquid helium cryostats or resistive heating stages. Magnetic or electrostatic actuation may replace piezoelectric drives in extreme conditions. Vibration isolation relies on passive springs or active cancellation systems, as vacuum environments transmit vibrations more efficiently than air.

**Comparative Technical Specifications**

| Parameter | Humidity/Temperature AFM | Vacuum AFM |
|-------------------------|--------------------------------|--------------------------------|
| Pressure Range | 1 atm ± 5% | 1×10⁻⁹ to 1×10⁻³ mbar |
| Temperature Range | -20°C to 300°C (standard) | 4 K to 1000°C (with options) |
| Humidity Range | 5% to 95% RH | Not applicable |
| Drift Rate | < 1 nm/min (stabilized) | < 0.1 nm/min (UHV) |
| Resolution Limit | ~1 nm (ambient) | Atomic resolution possible |
| Cantilever Requirements | Coated for humidity resistance| High stiffness, UHV-compatible |

**Applications and Limitations**
Humidity/temperature AFM excels in studying hygroscopic materials, polymers, and biological samples, where environmental response is critical. However, condensation can obscure features, and thermal expansion may distort measurements. Vacuum AFM provides pristine conditions for semiconductors, 2D materials, and surface science, though sample preparation is more demanding, and biological specimens are often incompatible.

Both systems require careful calibration. Thermal AFM chambers need periodic verification of temperature gradients across the sample, while vacuum systems require checks for vibrational coupling between pumps and the scanner. Manufacturers now offer modular designs, allowing users to switch between configurations without replacing the entire microscope.

Future developments focus on improving stability during rapid environmental changes and integrating spectroscopic techniques like Raman or infrared microscopy. Hybrid systems combining vacuum transfer with controlled gas introduction are emerging for catalysis research. These advancements ensure AFM remains versatile for nanomaterial characterization across diverse conditions.

In summary, specialized AFM configurations with environmental control push the boundaries of nanoscale metrology. Whether probing water adsorption on polymers or atomic defects on graphene in vacuum, these systems provide the precision needed to correlate structure with environment-dependent properties.