The Concentration Measurements of Tellurium Donor Impurity in Lamellar Bismuth Samples by the Time-of-Flight Mass Spectrometry Method

Authors D.Yu. Matveev , D.V. Starov

Astrakhan State University, 20a, Tatischev St., 414056 Astrakhan, Russia

Issue Volume 11, Year 2019, Number 2
Dates Received 26 November 2018; revised manuscript received 08 April 2019; published online 15 April 2019
Citation D.Yu. Matveev, D.V. Starov, J. Nano- Electron. Phys. 11 No 2, 02017 (2019)
PACS Number(s) 82.80.Rt, 73.50. – h.
Keywords Bismuth (9) , Tellurium (3) , Thin films (60) , Mass spectrometry, Donor impurity.

The possibility of determining in-depth distribution of tellurium donor impurity in lamellar bismuth samples using the time-of-flight mass spectrometry and electron microscopy methods in the concentration range of 0.005-0.150 at. % Te is studied in the present paper. To measure the amount of tellurium in lamellar bismuth samples, we used a LUMAS-30 time-of-flight mass spectrometer with a pulsed low-pressure glow gas discharge in a combined hollow cathode and a Zeiss Evo-40 scanning electron microscope. The samples for measurements were cut from the middle of the ingots of the Bi-Te alloy with the required impurity concentration. The samples presented a thin plate of a size of 10 × 10 mm2 and 1 mm thickness. The samples were thoroughly washed in distilled water and then etched in a 65 % solution of nitric acid to remove the surface layer with traces of external contaminants. The samples were strengthened as the bottom of the hollow cathode in the gas-discharge cell, where the impulse ionization of the sample atoms in a glow discharge plasma occurred. The relative error in the in-depth distribution of impurities did not exceed 6 %, while the error in determining the concentration of impurities by a mass spectrometer, according to the passport data, did not exceed 5 %. The sensitivity limit in determining the concentration of impurities in the device LUMAS-30, according to the passport data, was 10 – 6 at. %. As a result of research, we set that the time-of-flight mass spectrometry method gives a very accurate determination of the tellurium impurity concentration, and also allows to establish a uniform distribution of tellurium over the volume of a doped bismuth lamellar sample. The electron microscopy method using a Zeiss Evo-40 microscope does not give a uniform distribution of tellurium over the sample volume.

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