How to write and read printable ASCII characters to/from UTF-8 encoding file?

I want to write to a file with UTF-8 encoding containing the character 10001100 which is Œ the Latin capital ligature OE in extended ASCII table,

zz <- file("c:/testbin", "wb")
writeBin("10001100",zz)
close(zz)

When I open the file with office(encoding=utf-8), I can see Œ what I can not read is with readBin?

zz <- file("c:/testbin", "rb")
readBin(zz,raw())->x
x
[1] c5
readBin(zz,character())->x
Warning message:
In readBin(zz, character()) :
incomplete string at end of file has been discarded
x
character(0)