LIBS-оценка содержания элементов по глубине образца
Для решения задачи воспользуемся программой Profile Builder.
Depth Profiling on LIBS
Overview
It is possible to configure the Z LIBS analyzer to report spectra from different layers in a material. This
can allow some qualitative depth profiling of a multi-layer material. It is important to note that the Z is
not intended to allow quantitative depth profiling. There are a few caveats to taking depth
measurements by LIBS:
- Не существует простой зависимости между числом лазерных импульсов и количеством удаленного в результате абляции материала образца.
- Для единичного выстрела позиция фокуса определена , обычно это поверхность образца. Каждый последующий импульс удаляет из глубины кратера меньше материала. Так как диаметр луча составляет ~50 мкм, этот эффект скорее всего не будет существенным в пределах первых 50 мкм абляции.
- As the crater is dug deeper, each pulse will remove
First, a few figures of merit:
- The laser spot is ~50um diameter
- A typical alloy raster includes 26 pulses/location; geochem and other materials 6
pulses/location.
- A typical alloy raster will remove 1-5um of heavy (non-Al) alloy, 5-10um Al alloy.
- 300 pulses per location has been shown to remove 80um Al alloy
- Crater sizes on pressed powders or irregularly shaped surfaces will be highly variable due to
differences in laser absorption, sample density, and sample cohesion.
SciAps recommends using ProfileBuilder PC software to do depth profiling and spectral interpretation
due to the ease of changing parameters and inspecting data.
Set Up Depth Profiling
Connect to Profile Builder and visit Testing and Results. Click Acquisition Settings.
Recommended Settings
-
Num of Locations – Start with 1. Move the sample if needed, as rastering is not as useful for
depth measurement.
- Cleaning Shots – 0 is recommended, since you can treat a surface contamination layer as an
additional layer to probe. Feel free to increase once you are comfortable understanding the
pulse number vs. depth relationship.
- Data Shots – an example is below with 50. This number should be an integer multiple of Num
Shots to Avg (5 * 10 = 50, where 10 is an integer).
- Test Rate and Clean Rate – 10Hz recommended. 50Hz test rate forces Num Shots to Avg to be 2n
with a minimum of 4 (e.g. 4, 8, 16, 32, etc.).
o Note that older Z-300s are limited to 10Hz Test Rate
- Linear (not random) – spectra will be grouped in order, not in random order
- Avg. Spectra – checked