Two-dimensional dopant mapping using secondary electrons in a scanning electron microscope (SEM) is a useful and rapid technique for studying dopant distributions with high spatial resolution in semiconductor materials and devices. However, the technique has a major drawback: although p–n junctions and differently doped p-type regions can be imaged, the contrast from differently doped n-type regions is extremely low, hence, such regions cannot normally be detected. We demonstrate that energy filtering of the secondary electrons substantially enhances the contrast of differently doped n-type regions, so that they are easily differentiated and mapped. This is because the contrast is based on the shift of energy spectra from n and p regions rather than secondary electron yield differences that lead to the conventional dopant contrast. We have used a standard commercially available Schottky field emission gun SEM for our work. Energy-filtered secondary electron imaging in a SEM therefore provides a rapid technique for the imaging and mapping of both p-type and n-type dopants. Our initial results indicate that a spatial resolution of <6 nm can be expected for favorable specimens.

Although dopant contrast in the scanning electron microscope has been known for a long time, its quantification is still a matter of debate mainly due to the lack of understanding of the contrast mechanism. Here we show that dopant contrast can be usefully increased at low extraction voltages. The effect may be related to the different angular and energy distribution of secondary electrons emitted from the p and n regions and for quantitative work should be studied over the full range of extraction potential.

Semiconductor dopant profiling using secondary electron imaging in a scanning electron microscope (SEM) has been developed in recent years. In this paper, we show that the mechanism behind it also allows mapping of the electric potential of undoped regions. By using an unbiased GaAs/AlGaAs heterostructure, this article demonstrates the direct observation of the electrostatic potential variation inside a 90nm wide undoped GaAs channel surrounded by ionized dopants. The secondary electron emission intensities are compared with two-dimensional numerical solutions of the electric potential.

In situ substrate cleaning by ion etching prior to deposition in physical vapor deposition processes is a key step in achieving good film adhesion, which is essential for all coating applications. Irradiation with metal or gas ions alters substrate surface chemistry, topography, and microstructure thus affecting subsequent film growth. This study compares Ti1−xAlxN/ferritic steel (x=0.54) interfaces formed after Cr ion bombardment at negative substrate biases, Us, ranging from 600 to 1200 V during a Cr cathodic arc discharge, stabilized with a 0.06 Pa Ar background pressure. Samples biased with −1200 V in an Ar glow discharge at a pressure of 0.6 Pa were also investigated. Microstructure and microchemistry of the interfaces was studied by scanning transmission electron microscopy with energy dispersive x-ray analysis using cross-sectional samples. Cr ion etching with Us=1200 V resulted in a net removal of over 100 nm of substrate material with the formation, through implantation, of a Cr-enriched near-surface region extending to a depth of ∼10 nm. As Us was reduced to 600 V, Cr accumulated at the surface as a ≳5 nm thick layer. Ar was incorporated at the surface to levels of 4–6 at. % during both Cr arc and Ar glow discharge etching. The microstructure of Ti1−xAlxN overlayers was dramatically affected by pretreatment procedures. Ar sputter cleaned steel surfaces (Us=1200 V) promote nucleation of randomly oriented grains leading to a competitive column growth with small column size and open boundaries. In contrast, Cr irradiation at the same bias voltage results in local epitaxial growth of Ti1−xAlxN on steel and lead to a superior performance in scratch testing compared to coatings deposited after Cr treatment with Us=600 V or Ar ion bombardment at Us=1200 V. Critical loads were 63, 47, and 27 N, respectively.

Emission spectra analysis of arc plasma for synthesis of carbon nanostructures in various magnetic conditionsCr ions generated by a steered cathodic arc discharge are utilized to control and enhance the adhesion properties of 3.5 m thick Ti x Al (1Ϫx) N based coatings deposited on high speed steel substrates. A two-step etching procedure ͑negative substrate bias, U S ϭ1200 V͒ is suggested, operating the arc discharge initially in an Ar atmosphere (p Ar ϭ0.09 Pa, 6.75ϫ10 Ϫ4 Torr͒ to achieve predominantly metal removing effects ͑etching rate: 9 nm min Ϫ1 ) with a mixture of Ar and Cr ions. In the second stage at residual gas pressure level (p Ar р0.006 Pa, 4.5ϫ10 Ϫ5 Torr, etching rate: 4 nm min Ϫ1 ) pure Cr ion irradiation leads to a Cr penetration as deep as 20 nm with a Cr accumulation of approximately 37 at % at the interface substrate/coating. This procedure promotes localized epitaxial growth of Ti x Al (1Ϫx) N and enhances critical load values up to 85Ϯ5 N.