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National Standard of the People's Republic of China
Germanium monocrystal-Inspection of dislocation etch plt densityUDC 669.783
:621.315.592
GB5252—85
This standard is applicable to the measurement of dislocation density or other defects of N-type and P-type germanium single crystals or slices with dislocation density of 0~100.000cm-2. The observation planes are (111), (100) and (113) planes. 1 Definition
1.1 Dislocation
In a single crystal, some atoms slip under the action of stress. The boundary between the slipped part and the non-slipped part is the dislocation line, referred to as dislocation. 1.2 Dislocation density
The total length of dislocation lines within a unit volume is called dislocation density (cm/cm\). This standard refers to the number of dislocation corrosion pits on a unit surface (pcs/cm2).
1.3 Dislocation pile
If the dislocation density of a certain area is more than five times higher than the average dislocation density of other areas of the section, and its area is more than five times larger than the area of ​​the field of view, then this area is called a dislocation pile (Figure 1): 1.4 Flat-bottomed pits
After chemical etching of a single crystal, in addition to dislocation corrosion pits, there are some shallow pits, which are called flat-bottomed pits here. It may be caused by factors such as vacancies or crystal inclusions (such as SiOx) (Figure 2). 1.5 Low-angle grain boundary
The interface of small grains with very small orientation differences in a single crystal is called a low-angle grain boundary. It is required that there are more than 15 dislocation corrosion pits within a length of 1mm and the length is more than 1.5mm. The dislocation corrosion pits on the (111) plane are arranged in a series of corners with the bottom edge facing each other (Figure 3). 1.6 Slip line (dislocation row)
The line formed on the crystal surface due to slip along the slip plane is called a slip line or dislocation row. It is required that there are more than 15 dislocation corrosion pits within a length of 1mm and the length is more than 1.5mm. The slip line of the (111) plane, the dislocation corrosion pits are arranged in a row in the direction of <110), and the bottom edge of each corrosion pit is on the same true line (Figure 4). 1.7 Star structure
Many dislocation corrosion pits are arranged in a triangular or hexagonal star structure on a macro scale (Figure 5). 1.8 Inclusions
Heterogeneous particles exist in the crystal.
2 Principle
The selective chemical etching method is used to display the dislocation corrosion pits. The principle is based on the distortion of the lattice around the dislocation. At the outcropping of the crystal surface, it reacts faster to certain chemical corrosive agents, resulting in the formation of corrosion pits with a certain shape. Therefore, the number of corrosion pits per unit area is used to represent the dislocation density N, (cm-1). N
Published by the National Bureau of Standards on July 22, 1985
Implemented on July 1, 1986
Where: s—viewing field area, cm2,
GB5252—85
—the number of dislocation lines passing through the viewing field area S. 3 Sample preparation
3.1 Directional cutting
Cut the crystal perpendicular to the growth direction of the single crystal, and the crystal orientation deviation is required to be less than 6. 3.2 Grinding
Grind with diamond sand (M28) to make the surface flat and without visible mechanical scratches. 3.3 Display of dislocation corrosion pitsWww.bzxZ.net
3.3.1 Chemical reagents used (all chemically pure) Nitric acid (HNO,)
Hydrofluoric acid (HF)
Hydrogen peroxide (H,O,)
Potassium iron hydride [K,Fe (CN). )
Copper nitrate [Cu (NO,]]
Potassium hydroxide (KOH)
3.3.2 Chemical polishing
65~68%
30%,
>82%.
Use hot polishing liquid [HF:HNO,=1:1~3 (volume ratio) to polish to a mirror surface. 3.3.3 Etching
(111) crystal plane: In the etching solution [KFe (CN). : KOH:H,O=80g:120g:1LJ Boil for 5~10min, or without chemical polishing as described in 3.3.2, directly drop polishing etching solution [HF:HNO=1+4 (volume ratio)] on the cross section of the single crystal rod heated with boiling water, requiring the cross section to remain horizontal and to be exposed about 2mm above the water surface (the single crystal can be immersed in polishing etching solution). Etch until it is mirror-like.
3.3.3.2 (100) surface: Soak in etching solution [HF:HNO,:Cu(NO), (10%) aqueous solution = 2:1:1 (volume ratio)] for 5min. min.
3.3.3.3 (113) Surface: Soak in the etching solution [HF: H2O: Cu(NO2)2 (10%) aqueous solution = 2:11 (volume ratio)] for 10 min.
3.4 ​​Cleaning treatment
Wash the chemicals adsorbed on the crystal surface thoroughly with hot water, and wipe it dry with gauze or other wipes. Note: The above operations should be performed in a fume hood. 4 Equipment
4.1 Metallographic microscope: magnification 40 to 200 times, meet 5. 2. 4.2
Vernier caliper: accuracy 0.02mm.
4.3 Equipment for cutting and grinding single crystals.
4.4 Containers resistant to corrosion by HF, HNO, and other chemicals. 5 Measurement steps
5.1 Observe the sample with the naked eye to see if there are macroscopic defects and their distribution. 5.2 Selection of field of view: Place the sample under a metallographic microscope, estimate the dislocation density, and select the field of view area: N, 1mm for <5000cm2, 5000
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