---
title: "Cryo-SEM: Preserve Before You Observe Interactive Lab | Sandbox Physics"
description: "Can you distinguish freezing damage, frost, charging and beam damage?"
canonical_url: "https://sandboxphysics.com/labs/cryo-sem/"
language: "en"
page_type: "lab"
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  zh-CN: "https://sandboxphysics.com/zh/labs/cryo-sem/"
last_modified: "2026-10-27"
---

E23 · Frozen specimen workflow

# Cryo-SEM: Preserve Before You Observe

**Can you distinguish freezing damage, frost, charging and beam damage?** Yes, if you know the specimen's history, because each preparation step leaves its own kind of mark. Ice crystals mean the specimen was too thick to freeze fast enough. Frost is water vapor that condensed on the cold surface, for example during transfer. Charging points to a coating too thin to carry charge away, and beam damage grows with the dose received while imaging.

Take a specimen through freezing, fracture, sublimation, coating, transfer and imaging, in that order. Then trace each flaw in the final image back to the step that caused it.

> Interactive simulation: open this page in a web browser to change the parameters and run the model.

Model assumptions

This is a teaching workflow, not a preparation protocol, and its images are not measured micrographs. Freezing preservation, coating conductivity and beam damage follow assigned stand-in formulas. Surface ice exchange uses a flat-interface law with unit accommodation, fixed reservoirs and Murphy–Koop saturation. Heat transfer, nucleation, fracture mechanics, the microstructure of deposited layers and calibrated kinetics are left out. Each step keeps the settings it was done with, and later controls cannot repair earlier damage. Sizes and hardware are schematic.

Physics tutorial

## Cryo-SEM: Preserve Before You Observe

**Background** Before cryo-SEM takes an image, the specimen is frozen, fractured, partly cleared of surface ice by sublimation, coated and moved cold into the microscope. Each of these steps can leave its own artifact in the image.

**Why it matters** Freezing damage, frost, charging and beam damage come from different steps. A later step cannot undo an earlier one, so removing an artifact starts with finding the step that caused it.

Start with the essentials

- **Focus question**: Can you distinguish freezing damage, frost, charging and beam damage?
- **One-sentence intuition**: The history of preparation is part of the image.

### Core mathematical model

#### Assigned freezing preservation

$$
P_f=\exp\!\left[-\left(\frac{t_s}{\ell_f}\right)^4\right]
$$

The preservation depth is assigned: 10 micrometres for plunge freezing and 200 for high-pressure freezing. Thicker specimens keep less structure. The factor is a stand-in, not a probability or a promise of vitrification.

#### Surface ice exchange

$$
\begin{aligned}\dot h&=\frac{1}{\rho_i}\sqrt{\frac{m_w}{2\pi k_B}}\\&\quad\times\left[\frac{p_w}{\sqrt{T_g}}-\frac{p_{\rm sat,i}(T_s)}{\sqrt{T_s}}\right]\end{aligned}
$$

A positive thickness change means frost builds up; a negative one means ice sublimes. The gas and the specimen each keep their own temperature, and the reservoirs stay fixed.

#### Dose adds up with every image

$$
\begin{aligned}D_{\rm total}&=\sum_j D_j\\B&=\exp(-D_{\rm total}/D_c)\end{aligned}
$$

Each new image adds to the total dose, and structure fades exponentially with that total. The characteristic damage dose is assigned as ten electrons per square nanometre. Display gain does not change the dose.

### Common difficulties

#### What the model leaves out

**Typical misconception** If my settings pass the task, they will work on a real instrument.

**Better mental model** This is a teaching workflow, not a preparation protocol, and its images are not measured micrographs. Freezing preservation, coating conductivity and beam damage follow assigned stand-in formulas. Surface ice exchange uses a flat-interface law with unit accommodation, fixed reservoirs and Murphy–Koop saturation. Heat transfer, nucleation, fracture mechanics, the microstructure of deposited layers and calibrated kinetics are left out. Each step keeps the settings it was done with, and later controls cannot repair earlier damage. Sizes and hardware are schematic.

### Run the experiment

1. 01

   #### Freeze and fracture

   Choose Start a new preparation, select the freezing method and specimen thickness, then freeze and fracture the specimen.

   **What to observe:** Changing the method after freezing cannot repair ice-crystal damage.

2. 02

   #### Reveal and coat

   Choose sublimation temperature and time, commit etching, then coat the exposed face.

   **What to observe:** Remove too little ice and it hides detail; remove too much and structure is lost.

3. 03

   #### Protect the transfer

   Set cold-stage temperature, residual water pressure and transfer time, then commit transfer.

   **What to observe:** Frost picked up during transfer is a separate artifact from the ice crystals formed during freezing.

4. 04

   #### Acquire sparingly

   Acquire, check the target, then acquire again or change display gain.

   **What to observe:** Each new image adds dose that cannot be taken back; display gain adds none.

Physical conclusion

Read the environment, specimen and collected signal together.

Fields & matter · Starter path

## From a field to an electron microscope

Map an electric field and steer a charged particle. Then find the electron's wavelength and use electron beams to see a crystal and a surface.

[Start here → **Make an Electric Field Visible** Move the probe around a dipole and check that the field always points downhill on the potential landscape. Observe · 8 min](https://sandboxphysics.com/labs/electric-field/)

1. [1 Make an Electric Field Visible](https://sandboxphysics.com/labs/electric-field/)
2. [2 A Charge Bending through Fields](https://sandboxphysics.com/labs/charged-particle/)
3. [3 Electron Wavelength & Voltage](https://sandboxphysics.com/labs/electron-wavelength/)
4. [4 Electron Diffraction & Reciprocal Space](https://sandboxphysics.com/labs/electron-diffraction/)
5. [5 TEM Bright Field, Dark Field & SAED](https://sandboxphysics.com/labs/tem-mode-selector/)
6. [6 SEM Secondary-Electron Topography](https://sandboxphysics.com/labs/sem-topography/)

[View the full path →](https://sandboxphysics.com/topics/fields-and-matter/#starter-path)