<span>This invention relates to hydrogenated carbon compositions. Hard carbon compositions are known to be obtainable from depositions in radio frequency (RF) plasma reactors, in direct current (DC) discharge, chemical vapor deposition (CVD) apparatus, or through sputter deposition in secondary ion chambers, or by direct excitation of carbon in primary ion devices. These materials hold the potential for varied and significant utility due to the expectation that such compositions will exhibit properties similar to those of diamond, such as extreme hardness. It is known, for example, to use a hard carbon film composition in combination with a silicon adhesion layer to provide a hard coating to protect magnetic recording media. Summary of the invention: The present invention relates to a composition of matter and a method for selecting properties such as hardness, atomic density, mass density, lubricity, wearability, electrical conductivity, adhesion, stress, permeability or crystallinity of the composition Formed, for example, in the form of a film on a substrate. An aspect of the invention is a method for controlling any of the properties of hardness, lubricity, wearability, atomic density, mass density, permeability, electrical conductivity, stress, adhesion or crystallinity of a composition. The method includes placing a substrate in a chamber. A formation gas is controllably introduced in the chamber which includes the elements carbon and hydrogen and an optional element chosen </span><span>from fluorine, silicon, boron, oxygen, argon or helium. The gas is controllably energized to have an energy on the substrate in a range from between about 30-200 eV. As a result, a composition is formed on the substrate having an density between that of pure diamond and at least 0.18 moles per cubic centimeter. The composition has the following basic formula:C.sub.1-z-w Si.sub.z A.sub.w [H.sub.1-x F.sub.x ].sub.ywhere: 0.ltoreq.z+w.ltoreq.0.15, 0.ltoreq.w.ltoreq.0.05, 0.ltoreq.x.ltoreq.0.10, 0<y<1.5 and, A is boron or oxygen. The chamber may be an RF plasma chamber, where the total gas pressure in the chamber is in a range of from 5 to 100 mtorr, the energy is the impact energy on the substrate and the energizing is controlled by controlling the RF bias voltage in a range from about 100-1500 V. The chamber may be a vacuum chamber, where the pressure is about one millitorr and energizing is obtained by means of an ion source. The ion source may be a primary ion source where the energy is the impact energy of the gas on the target, or a secondary ion beam system where the system has a first ion beam for producing at least a portion of the gas by sputtering from a target and a second ion beam for energizing the gas after the gas impinges upon a substrate. A feature of the invention is that the composition may be formed as a function of time, wherein the composition properties are varied to form different regions of the formed composition.http://www.google.com/patents?vid=USPAT5750210</span>