SEDL / STP / STP889-EB / STP32953S

Measurement of Hardness at Indentation Depths as Low as 20 Nanometres

Oliver, WC
Research scientist, Oak Ridge National Laboratory, Oak Ridge, TN

Hutchings, R
Staff member, University of Cape Town, Cape Town,

Pethica, JB
Staff member, Cavendish Laboratory, University of Cambridge, Cambridge,

Pages: 19    Published: Jan 1985

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Abstract

Hardness as a function of depth is examined over a wide range of depths in gold, nickel, lithium fluoride (LiF), and silicon. To examine hardness in very shallow indents (100 nm), a special hardness tester with 2.5-μN load resolution and 0.2-nm indenter displacement resolution was used. The tester monitors the load continuously as the load is applied and removed. The hardness is calculated using the depth measurements. Images of indents in the scanning electron microscope (SEM) and transmission electron microscope (TEM) are used to check that the expected contact areas are achieved. It is shown that the contact area can be calculated if elastic effects are accounted for. The loading and unloading portions of the curves are discussed in detail. Attention is paid to the mechanisms of hardness changes with depth and the effects of elastic recovery on contact area measurement.