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Sheet resistance is a measure of resistance of thin films that are nominally uniform in thickness. It is commonly used to characterize materials made by semiconductor doping, metal deposition, resistive paste printing, and glass coating. Examples of these processes are: doped semiconductor regions (e.g., silicon or polysilicon), and the resistors that are screen printed onto the substrates of thick-film hybrid microcircuits. The utility of sheet resistance as opposed to resistance or resistivity is that it is directly measured using a four-terminal sensing measurement (also known as a four-point probe measurement) or indirectly by using a non-contact eddy current based testing device. Sheet resistance is invariable under scaling of the film contact and therefore can be used to compare the electrical properties of devices that are significantly different in size. ==Calculations== Sheet resistance is applicable to two-dimensional systems in which thin films are considered as two-dimensional entities. When the term sheet resistance is used, it is implied that the current is along the plane of the sheet, not perpendicular to it. In a regular three-dimensional conductor, the resistance can be written as: where is the resistivity, is the cross-sectional area and is the length. The cross-sectional area can be split into the width and the sheet thickness . Upon combining the resistivity with the thickness, the resistance can then be written as: : where is the sheet resistance. If the film thickness is known, the bulk resistivity (in Ω cm) can be calculated by multiplying the sheet resistance by the film thickness in cm. : 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「sheet resistance」の詳細全文を読む スポンサード リンク
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