シート抵抗の単位；ohm per square; Ω/sq、文字化け？

Sheet resistance, Wikipedia

Sheet resistance is a special case of resistivity for a uniform sheet thickness. Commonly, resistivity (also known as bulk resistivity, specific electrical resistivity, or volume resistivity) is in units of Ω·m, which is more completely stated in units of Ω·m²/m (Ω·area/length). When divided by the sheet thickness (m), the units are Ω·m·(m/m)/m = Ω. The term "(m/m)" cancels, but represents a special "square" situation yielding an answer in ohms. An alternative, common unit is "ohms square" (denoted "{\displaystyle \Omega \Box }") or "ohms per square" (denoted "Ω/sq" or "{\displaystyle \Omega /\Box }"), which is dimensionally equal to an ohm, but is exclusively used for sheet resistance. 

スクウェアの□は文字化けかと思いました。

電気抵抗測定の3つの基礎知識、ナプソン