Business Segments - Schedule of Business Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Net revenues	$ 24,340	$ 23,100	$ 19,790	$ 17,975	$ 15,084	$ 15,227	$ 14,460	$ 20,692	$ 85,205	$ 65,463	$ 85,035
Operating income (loss)	1,296	$ 1,204	$ 171	$ 1,054	(1,181)	$ 31	$ (972)	$ 1,637	3,725	(485)	4,916
Capital expenditures									3,012	2,676	714
Depreciation and amortization									1,398	1,258	1,690
Identifiable assets	116,913				102,098				116,913	102,098
Continuing Operations
Segment Reporting Information [Line Items]
Capital expenditures									3,012	2,675	583
Depreciation and amortization									1,398	1,078	1,125
Operating Segments | Semiconductor
Segment Reporting Information [Line Items]
Net revenues									72,086	54,516	66,455
Operating income (loss)									8,585	4,168	8,744
Identifiable assets	70,631				51,648				70,631	51,648
Operating Segments | Semiconductor | Continuing Operations
Segment Reporting Information [Line Items]
Capital expenditures									2,264	912	379
Depreciation and amortization									905	821	828
Operating Segments | Material and Substrate
Segment Reporting Information [Line Items]
Net revenues									13,119	10,304	13,682
Operating income (loss)									278	684	3,641
Identifiable assets	19,541				12,717				19,541	12,717
Operating Segments | Material and Substrate | Continuing Operations
Segment Reporting Information [Line Items]
Capital expenditures									695	1,724	171
Depreciation and amortization									438	197	136
Non-Segment Related
Segment Reporting Information [Line Items]
Net revenues									0	643	4,898
Operating income (loss)									(5,138)	(5,337)	(7,469)
Identifiable assets	$ 26,741				$ 37,733				26,741	37,733
Non-Segment Related | Continuing Operations
Segment Reporting Information [Line Items]
Capital expenditures									53	39	33
Depreciation and amortization									$ 55	$ 60	$ 161