Eric Kay

Simple model for thin ferromagnetic films exchange coupled to an antiferromagnetic substrate

The exchange field Hex transferred from a thick antiferromagnetic substrate to a thin exchange coupled ferromagnetic film is shown to reach a limiting value no matter how large the exchange coupling is. The limit is due to domain‐wall formation in the antiferromagnet. Numerical results based on a simple model for the interface are presented and compared to experimental results.

Positive‐ion bombardment of substrates in rf diode glow discharge sputtering

The plasma potential and the potential of an electrically isolated surface are measured in an rf diode sputtering glow discharge. The influence on these potentials of both the geometry enclosing the discharge volume and of a positively biased auxiliary electrode in contact with the discharge is investigated. It is shown that confining the discharge increases the plasma potential and the energy of positive ions incident on electrically isolated substrates, whereas applying a positive voltage to an auxiliary electrode also increases the plasma potential but does not significantly increase the energy of ions incident on electrically isolated substrates. The effect of rf modulation on the ionic energy distributions is demonstrated. This occurs as the ions pass through the plasma‐substrate sheath and results in a large broadening of the energy distributions of low‐mass species.

Plasma potentials of 13.56‐MHz rf argon glow discharges in a planar system

The plasma potential of 13.56‐MHz low‐pressure argon glow discharges has been measured for various modes of applying the rf power in a geometrically asymmetric planar system. The plasma potential is determined from the energy distribution of positive ions incident on the grounded electrode. The voltages on the excitation electrode (target electrode) are carefully measured and the capacitive sheath approximation is used to relate these measured voltages to the measured plasma potential. This approximation is successful in most of the situations encountered in this low‐pressure (20 mTorr) relatively low‐power density regime. The effects of superimposing dc voltages on the excitation electrode are discussed.

GAS INCORPORATION INTO SPUTTERED FILMS.

The concentration of argon in sputtered nickel films has been obtained as a function of the film‐growth temperature, the discharge pressure, and of the energy (bias voltage) with which the argon ions bombard the growing film. The concentrations vary from about 10−1 argon atoms/Ni atom to 10−4 argon atoms/Ni atom, depending upon the conditions during film growth. The incorporation of both argon and nitrogen into nickel films is interpreted on the basis of results previously obtained from sorption studies in a more‐idealized system on a pre‐existing nickel surface.

PLASMA DIAGNOSTICS OF AN rf‐SPUTTERING GLOW DISCHARGE

The positive ions incident on the substrate plane in a planar diode discharge system are observed with an electrostatic deflection energy analyzer and a quadrupole mass spectrometer. Several targets have been rf sputtered in rare‐gas discharges and the mass spectra that are obtained indicate that the sputtered species, which leave the target predominantly as neutrals, are subsequently ionized in the discharge by Penning ionization rather than by electron‐impact ionization or other ion‐molecule reactions.

Ion-enhanced gas-surface chemistry: The influence of the mass of the incident ion

Abstract There are many examples of situations in which a gas-surface reaction rate is increased when the surface is simultaneously subjected to energetic particle bombardment. There are several possible mechanisms which could be involved in this radiation-enhanced gas-surface chemistry. In this study, the reaction rate of silicon, as determined from the etch yield, is measured during irradiation of the Si surface with 1 keV He + , Ne + , and Ar + ions while the surface is simultaneously subjected to fluxes of XeF 2 or Cl 2 molecules. Etch yields as high as 25 Si atoms/ion are observed for XeF 2 and Ar + on Si. A discussion is presented of the extent to which these results clarify the mechanisms responsible for ion-enhanced gas-surface chemistry.

Novel method for determining the anisotropy constant of MnFe in a NiFe/MnFe sandwich

We show that an in situ Kerr rotation measurement is a very effective technique for the study of antiferromagnetic (AF) ferromagnetic (F) film couples. Magnetic signals can be obtained even in the case where the (AF) is the top layer up to at least 200 A of AF thickness. We have used this in situ approach combined with ion milling to study the thickness dependence of the magnetic properties of Mn50Fe50/Ni80Fe20 systems. We observe that the exchange bias field has a surprisingly sharp onset at a critical thickness of AF∼50 A. We show that this is consistent with a simple model and that the magnetic anisotropy of MnFe can be estimated from the observed critical thickness to be ∼1.35×105 erg/cm3. The exchange field showed the predicted proportionality to the inverse of the F thickness from ∼50 to 400 A. Auger spectroscopy and spin polarized secondary electron emission have been used to rule out gross artifacts due to ion milling.

Glow‐discharge mass spectrometry—Technique for determining elemental composition profiles in solids

Glow‐discharge mass spectrometry, in which an rf glow discharge is used both to sputter etch the sample undergoing analysis and to ionize the neutral sputtered species, is shown to be a promising new technique for the elemental analysis of thin solid layers or bulk solids. A description of the method is given followed by some examples of its application to composition profiling. The influence of some parameters is shown and opinions as to the advantages and disadvantages of the method are given.

Plasma etching A ’’pseudo‐black‐box’’ approach

A framework for understanding plasma etching has been developed (using the CF4 plasma etching of silicon and silicon compounds as an example) which treats the discharge as a ’’pseudo‐black‐box’’ which is characterized by a dissociation rate G of the CF4 molecules and a recombination rate R at which CF4 and other inert molecules are re‐formed by recombination of the active fragments. Expressions based on the conservation of fluorine and carbon in the system have been derived which relate the concentration of the various species in the effluent gas to the etch rate. This approach provides a semiquantitative understanding of several aspects of plasma etching such as the effects of additive gases and the presence of a much larger ’’loading’’ effect for Si than for SiO2.

A New Technique for the Elemental Analysis of Thin Surface Layers of Solids

It is shown that the combination of rf glow‐discharge sputtering and mass spectrometry provides a very sensitive method for determining the composition of thin surface layers of solids. The sample is immersed in an rf sputtering glow discharge and a fraction of those sputtered atoms which are ionized in the discharge by Penning ionization are monitored with a quadrupole mass filter. 1011 sputtered atom/sec can readily be detected and considerable improvement in sensitivity can easily be anticipated. The sensitivity is comparable for all elements except He, Ne, and F and is independent of the matrix in which the species are contained; i.e., standards are not required. The matrix can be electrically insulating or conducting.